The only one I'm not especially thrilled with is gogo. He can do anything the other characters can do, but he does it all much weaker.

Otherwise I like them all, no matter how much everyone else hates them.

I never saw how anyone could complain about Relm. She's the strongest magic user in the game. She was my best character in my last playthrough, and even made the dragon's den easy. Strongest magic user in the game+gembox+economizer+quick+ultima. I didn't fear God.

Umaro is awesome. He makes the magic tower much easier. Who the hell cares if you can't control him when he hits for about 3000-4000 damage each turn and absorbs the most common types of magic? It's not like the lack of control makes him do stupid crap like cast life1 on himself, like other characters when you use them in the colosseum.

Gau is only bad if you're too lazy to find out what rages are most effective against which enemies. I'll admit i'm in that crowd, but I know better than to complain about him. And even I've discovered the usefulness of magic urn, Sr. Behemoth, stray cat, etc.

I was never a fan of mog because dance sucks, but I'd take him anyway because of the moogle charm. I then found out when I fought the undead dragon (can't recall the name. Skull dragon?) in kefka's tower that mog+holy lance+dragon boots=9999 damage against that thing. Turns out mog is pretty good after all. But moogle charm makes up for any amount of suckage mog would bring, regardless.

Setzer+fixed dice+offering=lots of dead enemies. Plus it's just cool to watch him spinning around and whipping dice and darts all over the place. Can't help imagining him bankrupting a casino in several minutes.

And how the heck could anyone hate Cyan, watching him with offering+gengi gloves going to town on a group of enemies, with about every 3rd hit dicing an enemy to pieces?

In short, there's no bad character. The only lackluster one is gogo. I always have a hard time deciding who else to leave back.