Arachnus X (Morph Ball Guardian)[edit]
As soon as it takes its form, pump missiles into its belly. If it scratches the air twice, be warned, because it's about to shoot a wave of energy at you, which does moderate damage. If it screams, jump onto a ledge nearby to dodge the fire. Once it's in its ball mode, you can't hurt it, so use a ledge to jump over it from high above. If it hits the wall you're clinging to, you'll fall and take damage. Simply repeat the process to make it transform back into a Core-X.
This part is fairly easy. If you ran out of missiles, grab the green X floating around, then hit the Core-X with a missile whenever it isn't flashing. Dodging it shouldn't be hard. Three missiles will finish it off easy, and now you have the morph ball!
Elephant Bird / Charge Core-X (Charge Beam Guardian)[edit]
At the start of the fight, just shoot the item sphere that the statue holds in its hands, then step back. The elephant bird will quickly transform into a Hard Core X. Don't collect the item though: the morph ball it holds is a fake that will cause a small amount of damage if you touch it. This fight is really just practice for the tougher Core-X form. All you have to do is keep from getting hit. When it is charging up to fire, it will open an "eye" - shoot it with a missile and then jump away immediately to avoid the blast. A few hits is all that is needed to kill it. Once it's dead, grab the giant X for the charge beam ability.
Zazabi X (High Jump/Jumpball Guardian)[edit]
To defeat this boss, you will need to dodge it until it opens its mouth and floats down slowly. Then, shoot 2 missiles as you can into it, and run away. If it eats you, bomb your way out. When all 3 segments of Zazabi's body are destroyed, it's mouth will become smaller, but every time it jumps you can shoot at it. Shoot 5 missiles into it's mouth and Zazabi will turn into it's core-X form. The Core-X is almost the same as with the Morph Ball Guardian, just a bit stronger and tougher.
Serris (Speed Boost Guardian)[edit]
This boss is Serris, who was infected and killed by an X parasite who took over its form. One of the more dangerous bosses, it moves quickly and inflicts great damage. Shoot its head with a missile or charged beam, then quickly jump out of the way. When the boss is shinesparking, he moves considerably faster than usual and is invincible to attacks. It may be hard to hit him, but watch his actions, dodge, and when you see him come at you, unload. The ladders to the left and right and on the ceiling are useful to dodge attacks. You can avoid virtually all of Serris' attacks by staying at the very top of the right ladder to make an easy (and boring!) fight.
Alternatively, you can crouch one block away from the door to avoid all attacks, though this can make the Core-X fight slightly more difficult, or hold onto the ceiling ladder directly above the 3rd platform and only drop down immediately after he does his waving attack. Make sure to jump back up after he finishes his arching attack.
The Core-X is better fought on land than underwater, since you can move more quickly up there.
B.O.X. Security Robot ("Super Missile Guardian")[edit]
Unfortunately, this boss will not give you any power-ups, since it's not X-infected. Hang onto the ceiling, and wait for it to come under you, then shoot. Its attacks include jumping at you (it cant hurt you, in this fight, if you're on the ladder when it jumps) and releasing a ball that opens a pillar of fire in both directions. Position yourself directly above the firebomb to avoid damage, but if you can't get there in time, when the flame lowers, move to the other side of it, since it comes back up before disappearing. Around 10-12 hits will make the robot go off to the side and create a passageway for you to follow.
Barrier Core-X (Varia Suit Guardian)[edit]
The Core-X who stole the Varia Suit became much bigger, and is sorrounded by a ring of tiny versions of itself. These can be destroyed but you should concentrate on the central Core-X. Missiles are useless here, so charge your beam and wait for it to go in your firing range. Make sure not to fall into the water, since that slows you down tremendously. The Core-X swings about the environment on curved swoops, and since it is so large and fast, it can be difficult to avoid damage. Keep your beam constantly charged and somersault jump when avoiding it when possible. That way, if you are unable to jump out of the way quickly enough, you will still inflict a hit with your mock Screw-Attack. After it changes color, hit it a few more times, and defeat the Core-X to claim what you deserve.
Scientist / Wide Core-X (Wide Beam Guardian)[edit]
He may look like a scientist, but don't be fooled! This is another Core-X, similar to the one fought when getting the Charge Beam. To get it to transform, just move close to it or shoot it. Charge your weapon and prepare to launch a shot at it as soon as the transformed X opens its 'eye'. Remember that you have limited time, so hurry up. After retrieving the Wide Beam, step onto the controls to cool down the heating unit and stop destruction.
Yakuza (Space Jump Guardian)[edit]
Yakuza is probably one of the most difficult bosses in the game. The battle is fought in a very tall, relatively thin silo, and Samus has the run of the floor while the large spider quickly scuttles above her. Samus must repeatedly fire missiles into the creature's open mouth in order to defeat it.
Yakuza makes his entrance shortly after yours - a distant explosion, followed by three balls of fire which burn for a short period of time in the far corners and one in the middle of the floor. Stand in the centre of the room and fire a missile upwards then move out of the way to get some early damage in. Yakuza will then will Space Jump around above you in a logical but unfixed pattern. Occasionally he will stop and open his maw for a few moments in order to spit more fireballs out. It is at these points that Samus must quickly fire as many missiles as possible in order to damage him.
Aside from these times, he is invulnerable. Your biggest worry is avoiding him. If he gets relatively above you, he will seize Samus and slowly pull her up to the top of the silo before slamming her down. As he pulls Samus up, he will sap her health and the poisons make it difficult for Samus to resist. Rapidly button bash as he draws her up to reduce the time he has a grip on you. Either way, Samus will take substantial damage from this attack. The impact also causes Samus to bounce from the ground as she slams into it, and you must be quick in getting out of the way after this happens, as he can very easily pick her up again!
Morphing into a ball and/or standing in the corner will help you avoid this. However, be aware that the fire that spits out and causes Samus to bounce up when in contact, sometimes pushing her right into Yakuza's pincers. Also the fire reduces the area in which you can run briefly; jumping is dangerous, again as you can cause Samus to leap right into his mouth.
After you have fired enough missiles (Yakuza will change colour and will become faster) his legs will drop off and he will somersault at ultra-high speeds in succession in order to 'fly' above you, spitting chunks of mass in order to damage Samus. He is also invincible when spinning. His mouth, however, is permanantly open. Standing in a corner and shooting upwards constantly will often be enough to damage him and destroy any of his incoming attacks. He will then turn into the usual Core-X.
Nettori (Plasma Beam Guardian)[edit]
So, the auxiliary power is on, but the Main Reactor Silo is still offline. Remember the roots in the Central Reactor Core. Nettori is the source of them. You should start the fight by jumping onto the right-hand platform, morph-balling at the left-hand side to avoid its spores, and using power bombs on it. When you are out of power bombs, move into a crouching position and use missiles on it. When it shoots spores at you, turn back into the morph-ball. Repeat these first actions until its head falls off.
If you fall into the samus eaters in the room, don't button mash-because you don't have the gravity suit yet, the water in the samus eaters will hold you down. Instead, hold A for 1 large jump and get back onto the platforms.
Keep blasting it with missiles. You now have to worry about the plasma beam shots it fires. It will fire high if you're jumping, and low if you're crouching, so do the reverse to avoid the shot. Continue blasting it with missiles and it will die and turn into a Hard Core X. Dispatch the X to receive the Plasma Beam and control over the doors and elevators in the station.
Nightmare X (Gravity Suit Guardian)[edit]
Remember that shadow you saw floating around in Sector 5 (ARC)? It was Nightmare's shadow. He has caused too much destruction in Sector 5 (ARC), and must be destroyed. His location cannot be confirmed, so you have to find him yourself. He is pretty easy to find. When you first go through the eye door, use a power bomb. Jump into the little morph ball passage, and grab an energy tank. Then fall through the fake floors, and Nightmare will rise.
To begin the fight, you have to destroy his gravity manipulator. To damage the manipulator, you can lure Nightmare up by jumping high, then coming down and getting a shot or two at it using a charged beam or a missile. Alternatively, you can stay under Nightmare in its first phase, as Nightmare only stays in one spot while hovering horizontally, and whenever Nightmare would come down, you could roll into a Morph Ball and stay out of harm's way, then come back and shoot the manipulator with more missiles and charged shots. Once it has been sufficiently damaged, he will start using his gravity manipulator, which will make your jumps lower, space jumps impossible, your run slower, the room wavy, and render your missiles almost useless, stopping and falling mid-flight, forcing you to fire charged shots or fire missiles point blank. When the manipulator is destroyed, his mask is destroyed, exposing his hidious face.
Now you have to blast missiles at his face. You can only blast him from the side, not from above or below. Get onto the ladder and shoot at his weak spot. When he is just about to hit you, get off the ladder when theres a gap in the laser shots. He will then fly around the room chasing you-space jump around him until he gets to the middle right area of the room. If he hits you he'll keep flying around the room. Get back onto the ladder and resume blasting more missiles into his face. Eventually he will turn into a usual Core X.
Destroy the rampaging bio-weapon to recover the gravity suit and escape from the flooded areas of Sector 5.
B.O.X. Security Robot X (Wave Beam Guardian)[edit]
Yes. He is back. While trying to enter the Restricted Zone, you discover you need the wave beam to enter. So you go back a few rooms, and you hear some familiar music. It's B.O.X. time! First, use a power bomb, to show a ladder on the ceiling. Grab on to it, and shoot B.O.X. with missiles. Don't fall into the water, because it is electrified by the damaged robot. Instead of shooting bombs, it shoots homing missiles, which take 40 energy each, though they can be easily destroyed with plasma beam shots. Staying in the right hand corner and firing at it diagonally can be helpful as it's jumps can't hit you in that area. When you pound it with enough missiles, instead of wossing out like he did in Sector 3 (PYR,) he will explode and turn into a giant brain, and then a Hard-Core X.
Neo Ridley (Screw Attack Guardian)[edit]
This shrieking form of Ridley is actually the resurrected clone from Other M copied by the X. You'll need to watch out for this massive creature as it flies about the room as it'll constantly be trying to fly into Samus. It'll be difficult to avoid colliding with the monster, most of his attacks take over 50 energy, and he takes over 110 missiles to defeat. His fireballs are indestructible and his tail is difficult to avoid. If Ridley grabs you and flies upward just keep firing away with Super Missiles to pound the beast. Every missile or two you hit him with, he will make a piercing screech. Seriously, don't use headphones during the battle if you want to come out with your hearing. After quite some fighting time, Ridley is finally defeated, and turns into a usual Core X.
Alternatively, you can fire charged beam shots diagonally through his body. Ever since getting the plasma beam, your beam shots do damage for every frame they're inside an enemy, and with Ridley's large hitbox, that racks up to quite a bit of damage. This requires more precision to optimize, but even if you miss a few shots, you should have him down much more quickly than firing missiles.
SA-X[edit]
You have had plenty of encounters with this guy before (5 of them). Now that you have the plasma beam, it's time to fight him. You fight him in the main room in the Operations Deck. The way to beat this guy is to blast him with an ice missile to freeze him and then follow up quickly with a charged plasma beam. If you do enough damage without dying, the SA-X will lose stability and he turns into a hybrid of Samus' suit and the hornoad he infected at the start. Blast it in the face with Charge Beams and stand 2 blocks away from it so its jump goes straight over your head. Defeat this monstrosity and he will turn into an ice beam Core X. If you run low on health/missiles, screw attack through the core-x to send a bunch of parasites flying. When you finally defeat your nemesis, you recover the ice beam...or not as he/she/it runs away into a collapsed vent. It doesn't matter though-you can now go to the operations deck to activate the self-destruct and besides, it's not like you're going to be fighting any metroids, right?
Omega Metroid[edit]
While you are escaping from the B.S.L. you encounter this guy in your ship area. First, just let him hit you with his claws. This will wipe out all of your energy except for 1 unit. If you had atleast 302 energy, it would take more than Mother Brain's hyper beam from Super Metroid. It will look like you are screwed, but the SA-X shows up, and shoots the Omega Metroid. It gets hit by the same claws, and dies. Now absorb the X parasite, and blast away to his stomach. Watch out for his claws. They are still pretty deadly. They take 1 tank now. It will die with normal shots, and it is the best way to kill it. Remember, you only have limited time to beat this guy. If you stay focused, this fight should be pretty easy. This is the final boss.