Ok many of you are probably thinking what? You dumbass! But he kinda did save konoha in a way. See Danzo planned on taking all of konoha under his control BUT before he could even start his plan Sasuke came and killed him. Now don't misunderstand I'm not trying to say Sasuke is gonna be a good guy and plant flowers with sakura and naruto I'm saying in a way he saved the leaf village... just a little