When you think of Final Fantasy villains, who immediately comes to mind? If you were playing games in the PlayStation 1 era, no doubt Sephiroth will be the first one you think of. But while he is doubtless the most famous villain of the series, he is far from the greatest villain Final Fantasy has to offer. That dubious honor instead falls to Kefka, the main antagonist of Final Fantasy VI.
[Note: Heavy spoilers from here on out.]
The first time you meet Sephiroth, he kills several floors of people in a skyscraper and then the president of a company. The first time you meet Kefka, however, he is little more than a joke—an ineffective ambassador that no one takes seriously. Yes, he sets a castle on fire. But after his plan fails, he is such a non-threat, you leave him stranded in the desert—paying little attention to his impotent threats of revenge as you ride away.
But this is all to lull you into a false sense of security. For the next time you see Kefka, he kills an entire kingdom by poisoning their water supply. He kills thousands—men, women, and children all killed. He leaves an entire country a graveyard simply because he is bored and wants to go home.
Over the course of the first half of the game, he burns cities, kills his own allies, and commits a second genocide (this time on the magical creatures known as Espers)—and uses you to unwittingly help in that plan.
And then he wins.
That's right, unlike pretty much every game ever made, the bad guy wins in Final Fantasy VI. Kefka becomes god, remakes the world by killing millions (if not billions), and leaves your party beaten, broken, and scattered to the four corners of the post-apocalyptic wasteland he has created. From then on, he just chills on the top of his enormous tower, killing randomly with his god powers whenever it strikes his fancy, just because he can.
Sephiroth? He killed a party member, burned down a town, and tried (and failed) to drop a meteor on a city. Evil? Sure. But it's like comparing a candle to a forest fire.
But what the most important thing is in all this is how you, the player, react to Kefka and all that he's done. You hate him. Just pure, unmitigated hatred. There is no other possible reaction you could have toward him.
You can feel sorry for a bad guy like Sephiroth—he is a fallen hero. He is a person who desperately searched for his place in the world and the meaning of his birth. Finding the answer to these questions, unfortunately, drove him insane and left him bent on destroying the entire world.
Kefka has no deep tragic backstory. Kefka is just a psychotic asshole. While Sephiroth has good in him, or at least did in the past, Kefka has not a single solitary redeeming virtue. Like the Joker in The Dark Knight, Kefka is a man who just wants to see the world burn.
But when it all comes down to it, what makes Kefka such a great villain is more than just the hate he garners. He transcends from a villain you hate into a villain you love to hate. Every time you fight him or otherwise spoil his plans, your level of satisfaction—your elation at victory—is far beyond what you feel when defeating villains in other games. And it is the way he plays on your emotions that makes him the greatest video game villain of all time.