StarCraft: Brood War/Protoss Mission 7: The Insurgent

Walkthrough
The real Aldaris is at the very top of the map. Attacking the other two will make Aldaris taunt you, but is otherwise useless. Anyway, you start this mission with a decent base and a selection of Dark Templar and Dark Archons. However, the High Templar have sided with Aldaris, so the High templar and Archons are unavailable. Enemy attacks are fairly powerful; they will be using Archons, Zealots, and Reavers. However, most of these can be blunted easily with the Dark Archon's Mind Control ability. Claim those Archons for yourself and turn the tables! Quickly build up some Photon Cannons at the entrance, since the few you have won't cut it. Also remember that the computer loves to sneak air units over your walls to wreak havoc, so put a few cannons on each side. Also, while the dragoons on the raised platforms make a nice early warning system, they'll be better at defense if you pull them back.

Build up a small team of Zealots and Dragoons, any Archons you can capture, and a Probe, and move northwest. You'll come to a place with two bridges. The one on the left leads straight to an enemy base, so put up a few Photon Cannons to block it. It'll save you trouble later. Then move your army across the other bridge and clear out the defenses around the mineral fields, if any. Secure it with some Photon Cannons in case you need the resources. Don't forget to take two or three Archons with you, so you can Mind Control the attacking Scouts, which will come at you immediately. When pulled off early enough, there will be no other enemy units at first, so a single probe and the Dark Archons should suffice. Move some units later into the expo for added defense.

Now you have at least two options. Crush Aldaris mercilessly with an overwhelming army, or do a quick but powerful strike to kill only him. The first one involves using your newly captured resources to build up a group of scouts and carriers and do the usual smashing through defenses. Launching an attack from the west side by air seems to be the easiest way into his base. If you don't want to risk losing a force of this size, just get a huge group of dragoons (at least 48) as well as any Archons and enemy Reavers you've mind-controlled, and have them totally raze the map.

The second one is a variation on the classic "Reaver Drop." Get a pack of Shuttles (you can use four, but the more, the merrier!), and a pack of Dark Archons. If you have plenty of resources and weren't worn down by enemy attacks, build some Scouts for air cover. Load your Dark Archons into the shuttles, move as close as you can to Aldaris without alerting the Photon Cannons, and then order all of your Shuttles to unload on his platform. Send your Scouts in at the same time to draw fire. As soon as a Dark Archon hits the platform, use Mind Control on Aldaris. Instant win. Enjoy the ensuing cutscene and plot twists.

There's also a third option: build at least 16 Scouts, put them in two groups of about the same size, and move both at Aldaris with about one or two seconds between each other. With this strategy, there's a good chance that enough units arrive at the target and don't get frozen by the Arbiters or fried by the High Templars. This is way more cost-effective than a complete attack with Carriers, and you need less time building them. To pull this off, you need at least two Stargates for unit production, air defense and attack maxed out, shield upgrades, and all Scout upgrades at the Fleet Beacon (especially the speed boost). If you have enough materials, upgrade ground attack and defense, too.

Take note that the flying Beasts can be Mind Controlled. Doing so will give you a cheap patrolling unit, which also keeps its usual flying pattern when left alone, so you don't have to micromanage it. Unfortunately, it will be shot down on sight by enemy forces.