I'm confuse how this shit fly when you're the strongest shit in the universe.The MC’s friends and allies end up betraying him after he defeated the Demon King, everyone in his village gets massacred, got framed, and blamed for crimes he didn't do, he lost his mom, cousins when he was younger, and lost his older sister and unborn nephew when he was the hero, gets locked up and tortured physically, psychologically and sexually by the princess. He manipulates a goddess (who has an obsessive love for the MC) to resurrect him and he is highly motivated to give his false comrades the most agonizing and humiliating deaths imaginable. Where he becomes a vengeful, sadistic psychopath that brutally, mercilessly, and ruthlessly murders his victims.
I know it's a trope but there's a lot of plot armor not to get one-shot by the mc for betraying him when he has the power to kill the demon king unless his companion is just stronger than him.