Invincible is brought to the future to help defeat a tyrant ruling the world, who turns out to be the Immortal. In this timeline, Invincible has left Earth with his family and left the planet to the care of the Immortal. As time passed the Immortal became sadistic and evil, losing his connection to humanity. The Immortal begs Invincible to kill him which the latter did unwillingly.
From – Invincible #54