Oops, I Leveled Up the Apocalypse

Frank Ford arrives in a post-apocalyptic wasteland in the body of a nobody who is scheduled to be sent out and killed. The night before he is due to be handed over, the Wife-doting System activates for him. Given a choice of people to attach himself to, he picks three that everyone else has written off: Anna Hutt, an S-class squad captain who is paralysed, Bess Bruce, a mutant whose body came out deformed, and A77, a clone who is close to dying. The mockery lasts until he injects them with a serum. Anna's psychic ability comes back, Bess turns into a fighter who can hold a line by herself, and A77 wakes up able to teleport. The three of them tear through everything sent at them. Colonel Dylan Jones, high up in the Fortress City government, starts working against Frank behind the scenes, and what follows is missile fire and a manhunt running through the whole city.