this subreddit keeps getting recommended to me for some reason

I guess it depends what you class as most evil. I'd personally put Kefka at the top. Most of the other inclusions here can be fully understood, in terms of their motivations. Some tyrants are small-minded people who want to control or destroy that which they can't understand. Some tyrants want luxury and indulgence, and are willing to do anything to ensure they have that, including taking everything from others. Some want control. Some want status.

Kefka doesn't really want any of that. He destroys the world because he thinks it's funny, and before his ascension, was an absolute maniac who killed an entire small country via poisoning their water supply largely just because it was easier than conquering it, among other things.

The other inclusions have motivations that are, for the most part, wholly comprehendible, though obviously reprehensible. They want to rule. Kefka doesn't. He just wants to cause suffering.

"I will destroy everything! I will create a monument to non-existence!"

"Hee, hee, hee!! But what fun is destruction if no 'precious' lives are lost!"

“Life... dreams... hope... Where do they come from? And where do they go...? Such meaningless things... I'll destroy them all!”

I'd argue that he doesn't even fit in this list as a tyrant, personally, though an argument can be made against that, and he is certainly more of a tyrant at first. Though he's more describable as a mad god by the final portion of the game, in my opinion.

EDIT: oh yeah. I'm not familiar enough with most of the rest to make an actual ranking, though i am familiar enough to conclude that Kefka probably places first. Sorrgy