This is it. The big showdown. Let's do it.
Wasteland 2 guide: defeat Matthias and save the world
When Vargas volunteers to come along you should accept. As you approach the area you'll have to deal with a large Scorcher with 3500 HP. Use as much cover as possible and don't get too close or he will unleash the flamethrower.
Again, explosives, TNT, energy weapons and sniper rifles are the best weapons to use on large enemies so give it everything you've got.
Reload and recover and as you continue Matthias will begin ranting and explaining the backstory. Once he's done, fight the large group of enemies. Use grenades to thin them out but be aware there's not a lot of cover you can use here.
When they're all dead head into the Citadel to speak with Matthias. Take down the turrets near the elevator so you can go down a level. Reload and recover again - you're about to start the longest battle of the game, so make sure you're at your strongest. You should also take as much kit off Rose as possible…
When you exit the elevator Matthias will transform into the Cochise AI, which will affect the robots around him and Rose herself. Kill rose and get into cover.
A good tactic is to send your energy and sniper experts to the front, using them to take out enemies before pushing back to where you other members are to take down any spawning enemies. It's a toughie, and you'll need a stack of medipacks.
Save the World
Once this is all dealt with Vargas will tell you to go to Min's workshop and set off the nuke to stop the AI spreading. Go to the north corner and take the stairs to the locked door - use Computer Science to get through.
Here you can talk to Mercaptain, then head into the center room of the Ranger Citadel. The nuke is down the first set of stairs and in the room where you used to be able to buy explosives. Use lockpicking to get through and take your final decision in the game...
You can let General Vargas sacrifice himself, take the entire team with it or just leave one person behind.
Once the nuke explodes, watch the final cutscene - congratulations, you've completed Wasteland 2!