Trust me, I can come up with a bunch of twisted endings.

If he some how gets all his friends killed <Redacted because spoilers> he will stand on the roof top of the school, holding a gun in his hand. He will utter "I'll be with you guys soon." Scenes flash between the Persona 3 cutscene when the protagonist gets th evoker. Kami raises the gun to his head, shaking, before smiling. He utters "persona" in the same way as the protagonist of P3, and shoots himself.