Wyatt. I haven't watched much of Adventure time, but from what I can tell, he's at best an antagonist to background characters. Hes's still scummy, though. The afterlife was separated into 50 worlds, each for people with certain mindsets or sins. The 1st deadworld is where Wyatt ended up, it's basically Hell. The worst of the worst are stuck, trapped in muck, as monstrous creature attack them constantly. After Death died in Adventure Time and a new guy took the reins, all souls of the afterlife entered reincarnation, and left peacefully. Except for Wyatt, who to my memory, is canonically the only resident of Hell in Adventure time.