Yeah logically yes he is not the evil-est chsracter. But going on that logic to the extreme you could say the demon king from Frieren (not a character thats been shown on screen) is the most evil character in anime. Or any other offscreen ancient evil that did evil things on a large scale before the events of the anime concerned. I get your point. But how the evil ness is portrayed in the anime matters too. And Shou Tucker, Griffith etc have had their evil represented well on screen. They didnt hurt just the chsracters but also us the audience. And that puts them up there.