Regret? It's the Apocalypse!EP 38

A mysterious prodigy, said to have reached the peak of power at just ten, spends 30 years being a guardian, keeping enemies at bay and securing an era of peace. Over time, that peace is mistaken for goodwill. So the prodigy then gets cast out. Only after his departure does the truth begin to surface, but by then, it is already too late...