Ok, KingDaniel. But how would they explain it in a film? In ST2009 Spock Prime explained about Nero by vulcan mind meld and many people didnīt understand. Unless it has many flashbacks.
What needs to be established? Mitchell and Kirk were friends in TOS, they crossed the Great Barrier and Mitchell's eyes went funny and he got Telepathic powers. There's really nothing of Mitchell's history that needs to be explained, and they don't even need to make Mitchell and Kirk old friends.
He could just be sitting at a station on the Bridge without any introduction other than Kirk calling out his name and rank and asking for a status, and whatever causes Gary Mitchell to become the Villian happens.
One Day I hope to be the Man my Cat thinks I am
Where are we going? And why are we in this Handbasket?