StarCraft/Counters

Probe
This will almost never be used for military purposes, other than scouting, early harassment, or the dreaded "Cannon Rush" strategy. Each race can put up towers (Bunkers, Photon Cannons, etc.) to discourage Probe espionage.

Zealot
The Zealot is significantly more powerful than its Zergling and Marine counterparts, but it cannot attack air units. They remain useful into the late game, especially with their speed upgrade.
 * Zerg: Swarming with Zerglings or using "Hydralisk Dancing" techniques are generally effective. Lurkers work well when they are available, as does any air unit.
 * Terran: Firebats with Medic support work well, and Vultures are even better. Again, any air unit with a ground attack is effective.
 * Protoss: Zealots of your own with Psionic Storm or Reaver support work well. Scouts, Carriers, and undetected Dark Templar can attack with impunity.

Dragoon
The Dragoon is a staple of most Protoss forces, often seen backing up Zealots and Reavers.
 * Zerg: Swarms of Zerglings and Mutalisks are good counters because the Dragoon deals less damage to "small" units. The Defiler's Dark Swarm and the Queen's Spawn Broodling spells are good choices as well.
 * Terran: Marines and Medics, with their small size and full damage attack, are the best counter until Siege Tanks.
 * Protoss: Zealots can defeat an equal Dragoon force if left unchecked. Reavers and Psionic Storm are good support choices as well.

High Templar
The High Templar is a spellcaster with no attack, slow speed, and powerful spells. Any time it is unsupported and in the open is a good time to attack it.
 * Zerg: Small packs of Zerglings can take out lone Templar easily. Queens with Spawn Broodling are effective to pick off Templar in battle, and Ultralisks have enough hit points to absorb a few Psionic Storms.
 * Terran: The Science Vessel's Irradiate is a good choice, though unstacked Battlecruisers are strong enough to take Psionic Storm attacks without dying.
 * Protoss: The Dark Archon's Feedback spell works well, and Reavers can strike a far-off Templar with their long range attack. Dark Templar sneak attacks can also discourage Templar strikes.

Dark Templar
The main threat with this specialty unit is in its permanent cloaking effect. Once detected, its main advantage is neutralized (though it still boasts a powerful attack).
 * Zerg: Keep Spore Colonies (Sunken Colonies cannot detect) and Overlords near at all times. The Queen's ensnare can also reveal cloaked units.
 * Terran: Keep Missile Turrets and Science Vessels nearby at all times (additionally, the Vessel's Irradiate Spell works well). Comstat Stations are a short-term solution, but an experienced Dark Templar user can work around them.
 * Protoss: Build Photon Cannons around your base and bring Observers with your attack force.

Archon
The Archon has a tremendous (350 point) shield and a brutal splash melee attack, though it has little hit points. Shields take full damage from all enemy attacks.
 * Zerg: Use the Guardians' long range to take them out from afar. Try to keep the Archon at a distance whenever possible, and try not to use Zerglings or Mutalisks.
 * Terran: Obviously, the Science Vessel and its shield draining EMP are a perfect counter, though be ready to follow up with regular units to deal the final 10 damage. If science vessels are not available, vultures with some micro can destroy Archons as they do full damage to the Archon's 350 shield.
 * Protoss: Reavers and Carriers can deal heavy damage to Archons from afar, but be ready to support these units should the Archon get close.

Dark Archon
The Dark Archon is a dangerous spellcaster, but, like the Archon, has few hit points and high shields. Tempt the Dark Archon to mind control a unit, draining all its shields. Then, with 25 HP, it will be as good as dead.
 * Zerg: Maelstrom is always a threat, stunning all biological units in a certain area for 10 seconds. Spread out your units to avoid the worst, and try and kill it quickly. Spawn Broodling will not work on the Dark Archon as it did for the Templar (and the Dark Archon's Feedback can destroy Queens easily).
 * Terran: Tanks' range is three times greater than that of mind control. Using many mechanical units works. Yamato gun destroys one in one hit.
 * Protoss: Use Reavers for their range and power. Your own Dark Archons with Feedback can work well.

Scout
Scouts can attack air and ground, and are considered the best fighter craft, but their missiles are explosive and lasers deal 8. Most ground to air units will work against them when used in numbers, but multiple scouts can overpower static defenses and some ground units.
 * Zerg: There are two reasons why Mutalisks work: Scouts will be out numbered, and missiles deal only 14 damage to Mutalisks. Hydras with or without Dark Swarm can also be particularly effective, but multiple Hydralisks are needed for facing Scouts.
 * Terran: Goliaths can destroy Scouts easily. Two or three Goliaths (preferably with the range upgrade) can outmatch a Scout. The air is a different story. The Scout outnumbers and beats Battlecruisers and one Scout may even beat two Wraiths. However, one Yamato hit or cloaking the Wraiths will overpower the Scout.
 * Protoss: Scouts are easily countered by Dragoons, and maybe High Templar with Psionic Storm. To confront a Scout in the air, outnumber it with Corsairs, or use at least two or three Carriers.

Corsair
The Corsair is a fast air unit with a rapid, splash dealing air-to-air attack. These units have a special ability called the Disruption Web which cause enemy ground forces and structures to be unable to attack as long they're under the web's effect.


 * Zerg: The Devourers, with their heavy armor and Acid Spores, are best suited to countering Corsairs en masse. However, Corsairs will often show up extremely early in the game in a Corsair-Reaver or Corsair into Dark Templar combination, before Hive tech is feasible. In these circumstances, you must choose one or more Hydralisks, a Spore Colony, or Scourge to prevent Overlords from being killed. Floating all Overlords into a single cluster around a Spore Colony will render most Corsair harassment by small numbers of Corsairs ineffective, but will remove detection from expansions making them vulnerable to Dark Templars.
 * Terran: Battlecruisers and Valkyries, with their heavy armor, work best.
 * Protoss: Corsairs rip through Interceptors fast, so Carriers are a poor choice. In small battles where the Corsair's splash has less effect, Scouts can defeat Corsairs. Stick with Corsairs of your own, or try using a Dark Archon's Feedback.

Carrier
The Carrier is known for its 4 base armor, and its ability to run and attack at the same time. Heavy armor works well against them, as Intereptors only do 6 damage each.
 * Zerg: The Scourge are your best bet with 110 damage. The Carrier can barely fight back before its destroyed. Also, Devourers weaken its armor, and stand well against Interceptors.
 * Terran: Yamato gun if you have it, but cloaked Wraiths if they don't have Detection work the best. Ghost lockdown is also very effective.
 * Protoss: Scouts can work, but Scouts are generally not recommended. Lots of Dragoons, and even better, High Templar with Psionic Storm. It deals a massive 112 damage, and the Carrier is slow, taking much of the damage.

Arbiter
The Arbiter cloaks every friendly unit around it, but cannot cloak itself. Also, 10 damage explosive is not a lot. Zerg: Probably any anti-air unit, particularly Scourge. Just keep in mind, large groups of anything can be stasised, and large numbers of friendly units can be summoned for an offensive recall.

Drone
The Drone is the worker for Zerg. It is less common to see them as scouting units because a Zerg player almost always has numerous Overlords.


 * Zerg: Mutalisks are great for worker harassment, because they can hit and run fast, as well as damage more than one worker at a time with their unique splash attack.
 * Terran: In late game, Irradiate is good for taking out worker lines. Stacked cloaked Wraiths work well if the opponent is lax on their cloaking detection.
 * Protoss: The High Templar's Psionic Storm is an effective weapon that can kill nearly all of a player's workers with little warning. Reavers also make great worker killers because of their splash damage.

Infested Terran
The Infested Terran is probably the best suicide attacker in the game. Able to deal 500 points of damage, these units can kill any enemy ground units in a one on one fight. Their attacks also do splash damage, so its best used against groups of enemies.


 * Terran: Use large groups of Siege Tanks in Siege mode to stop these suicide attackers from causing harm to your units. Bunkers can be destroyed in one hit from Infested Terrans if they are not used properly.
 * Zerg: Groups of Guardians and Hydralisks are pretty effective at stopping an Infested Terran from causing trouble.
 * Protoss: Ground units like the Dark Archon and the Archon are pretty ineffective since all of the Protoss ground units can be easily killed in one hit from the Infested Terran's attack. Only use air units to try to stop these units before they cause damage, since Infested Terrans can't attack air units.

Overlord
The Overlord is most encountered scouting through the base to check on the enemies' tech. It is slow moving, and has no attack, but the Zerg player will often have plenty to spare.


 * Zerg: Mutalisks and Hydralisks are the best tools for chasing scouting Overlords away, as they are the best anti-air units in the Zerg arsenal.
 * Terran: Wraiths, Goliaths, Valkyries, and Marines are all good tools for killing/warding away scouting Overlords, though Valkyries are particularly well-suited to destroying groups of Overlords with their splash damage.
 * Protoss: Corsairs are generally most effective (especially against groups, like the Valkyrie), though Scouts and Dragoons are ample substitutes.

Zergling
The Zergling is the most basic Zerg unit, but don't underestimate its usefulness. At only 25 minerals and half a supply point per Zergling, a swarm of them can be amassed fairly quickly, and used for an early-game rush.


 * Terran: A lone Zergling can actually kill a lone Marine, but if you outnumber them, use stimpacks, and throw in some medics and Firebats, and you will have the advantage. Also, Siege Tanks in numbers can hold off small rushes of Zerglings. Or, use Wraiths or Battlecruisers.
 * Zerg: Counter them with equal or larger numbers of Zerglings and a few Hydras and Lurkers, or use Mutalisks and Gaurdians. Alternatively, try using a Defiler's Plague on a large group and bring in Hydras.
 * Protoss: Zealots match up well, especially with upgraded weapons, but don't use Dragoons. Also, use a Templar's Psionic Storm and Reavers when they are available.

Hydralisk
The Hydralisk is the bread-and-butter Zerg unit, similar in function to the Marine but stronger and with an explosive attack.


 * Terran: Use Marines and Medics; the Hydralisk does half damage to them, and they do full damage to it. Later on, large numbers of Siege Tanks can hold them off, and groups of Battlecruisers work very well.
 * Zerg: Counter them with masses of Zerglings, with the speed upgrade preferably. Lurkers can also work very well.
 * Protoss: Use Zealots with the speed upgrade, Reavers, or a Templar's Psionic Storm.

Mutalisk
The Mutalisk has the distinction of being classified as a "small" unit, meaning it takes 1/2 damage from explosive weapons, which are most anti-air weapons. Therefore it can be extremely useful, even later in the game. It also has a more balanced air/ground attack than its counterparts, and is very fast and relatively cheap.


 * Terran: Marines with the range upgrade and stimpacks, backed up by Medics, go through Mutalisks like a hot knife through butter. If you are forced to use Goliaths or Wraiths, make sure you have the range and cloaking upgrades, respectively. Valkyries do great damage to Mutalisk groups, but are hardly useful outside of this role, so don't go crazy with them.
 * Zerg: Try using a Defiler's Plague on stacked Mutalisk groups, and bringing in your own, or a group of Hydralisks with the Range upgrade.
 * Protoss: Groups of Corsairs work well, as does a Templar's Psionic Storm. If the enemy has large numbers of stacked Mutalisks, use an Arbiter's Stasis Field to discourage this kind of behavior.

Guardian
The Guardian has a vast range, and can often even take down other units with impunity (since they simply can't reach the Guardian), and can even take out Terran Missile Turrets without fear of being hit. However, they are slow and very vulnerable to air units unless you have Devourers, Hydralisks, or Mutalisks on your side with them.
 * Terran: Your best bet are Wraiths and Valkyries, if they have no anti-air with them. However, if they do, then bring Goliaths with a missile range upgrade. A science vessel with Irradiate (or even Valkyries) can do well if the units are heavily stacked.
 * Zerg: Dark Swarm and range-upgraded Hydralisks.
 * Protoss: Corsairs will easily take down these units, even if they have a couple of Devourers. Beware: you must micromanage your Corsairs to keep them spread out if they have many Devourers; they will slow your Corsairs down to the point of uselessness. Alternatively, a combination of High Templars with Psionic Storm and Archons will take care of them quickly if they're stacked.

Scourge
They're flying Infested Terrans, without splash. Best used against Carriers, since four or five can take them down before they even know what's happening. If the opponent is cloaking a Zealot army with an Arbiter, these can also give you a little help (even though it shouldn't matter because you have Overlords). Not much use in Zerg vs. Terran or Zerg vs. Zerg, since both of these races will usually have other units that will kill your Scourges too fast. However, it may be helpful to give these little guys a couple of points into fly carapace – they can take a couple more hits that way, and a couple more hits is a couple more seconds to get to the target.


 * Terran: Wraiths, Goliaths, or Valkyries will annihilate Scourges pretty quickly. A lone Battlecruiser may succumb to a few of these, though.
 * Zerg: Don't send out an army of Guardians or Devourers without Mutalisks or Hydralisks, and you'll be fine. Alternatively, more Scourges is also an answer.
 * Protoss: A few Scouts or Dragoons will kill Scourges pretty quickly – basically any anti-air with a higher attack than 10. A group of a few will kill them pretty easily. 6+ Corsairs can kill off all incoming Scourge.

Vulture
The Vulture, when speed upgraded, is the fastest unit in the game. There are many strategies that can be used with them, including hit and run tactics. This unit can be upgraded with Vulture Mines, which will annihilate any group using starting units – Zealots, Zerglings, Marines/Firebats/Medics, and in some cases Hydralisks. The hit and run also works great in a small micro between Vultures and another unit.


 * Terran: Wraiths, Battlecruisers, and Goliaths will tear through Vultures. Watch out though, as Goliaths will be brought to 1 or 2 HP from mines.
 * Zerg: Guardians and Mutalisks will work the best. Lurkers and Hydralisks together will also take them down. Another tactic is to spawn a Broodling on one of them immediately after they lay mines, which will cause a mine group to attack the Broodlings. After that, mine splash will take care of the rest.
 * Protoss: Dragoons work for early game, and obviously any air unit. Do not use Archons, as hit and run attacks against Vultures are ineffective. However Archons float and don't trigger mines.

Goliath
Think of the Goliath as a stronger and more specialized Marine. The Goliath's ground attack is not the most powerful, but has a good range, rate of fire, and deals 100% damage to all targets. Its anti-air missiles also do impressive damage. You should consider the Charon Boosters range upgrade for them to be mandatory. With it, they can match Gaurdians' range. One of the Goliath's downsides is its extremely poor pathfinding.


 * Terran: Marines are good at taking out unsupported Goliaths, as are Siege Tanks. Large numbers of Battlecruisers can work, but may take significant damage.
 * Zerg: Nothing tears through Goliaths quite like a Zergling group. Hydras can also work well, as they are more efficient against large ground units than Goliaths. Also consider Mutalisks, because Goliaths deal half damage to them, but not if the Goliaths have Marine support.
 * Protoss: Zealots with the speed upgrade and Dragoons with the range upgrade work well. Later on, use Reavers to deal massive damage to the Goliaths, or Dark Templars.

Battlecruiser
The Battlecruiser is an very expensive unit, but is arguably one of the Terran's strongest. It can serve many purposes, and is most effective in groups of six or more. These groups are extremely hard to stop. Also, the Battlecruiser can be upgraded to have the Yamato Cannon, which can do 260 points of damage, at the cost of 150 energy. Always accompany your Battlecruiser groups with Science Vessels, to provide defensive and offensive abilities and cloak detection.


 * Terran: You will be in for a fight either way. Try using packs of cloaked Wraiths against small Battlecruiser groups, or upgraded Goliaths. If you are facing a large group, counter with you own armada and target two Yamato Cannons on every one enemy Battlecruiser.
 * Zerg: Whatever you do, no amount of Scourge will be able to hit large Battlecruiser groups, and Hydras are generally too weak to stand toe-to-toe. Use the Defiler's Plague to severely damage the Battlecruisers, and bring in Devourers and Mutalisks to finish them. Hydras under swarm cause Battlecruisers to run.
 * Protoss: The Protoss have the best Battlecruiser counter: the Arbiter. A single Stasis Field can take 12 or more stacked Battlecruisers out of the picture, while you place Dragoons and Scouts around them to attack as soon as they are free. Also, large numbers of Photon Cannons can slow down a Battlecruiser group better than the other species' defenses. Or, use mind control on small groups.