The last mission before you complete the game is to decide whether or not to kill Trevor, Michael or have a death wish. That decision is left down to Franklin and for me, I choose to kill Trevor. Trevor died crashing his car into gasoline where Franklin shoots him and he burns to death.
But the good thing is, once Trevor has died and the mission is over, you get half his cut from the bank heist. I believe an extra 15 million on top of your 30 million. So really, killing Trevor is a good thing. But then you have the option of killing Michael or teaming up with both and taking out the F.I.B.
I’m glad I killed off Trevor, he was actually a horrible character, funny but horrible. You get a 40G achievement for ending the game, I’m not sure if you can obtain other achievements for choosing a different route to ending the game. So who did you kill?