I still love Kuja cause he was my fav character in the jap version, with that sensual voice and his nice spells, and of course with the memories I have from playing FFIX, he was a great villain...
But I agree with sdm42393, Square needs to play FFIX again >=( ... As I said in the VA thread, they Killed all the poetry, the sensuality and the arrogance of Kuja... they Killed Kuja...

About fighting him, I don't think he is really so hard to beat, Ultima can be annoying but dodging in the right moment can make u win the battle, cause when he casts Ultima he has to finish the attack even if it fails, so if u dodge and then attack him, he wont dodge, and will surely get damaged... If I remember well, in the jap version he didn't move when casting Ultima, in the Us version he can move, but anyways he is weak when casting, cuase he can't dodge an can't block while doing it. So, a little training on dodging and Kuja is a piece of cake ...
But, anyway, I think Flare star can be more annoying than Ultima or than Seraphic star...

I still don't get an annoying villain... maybe Chaos at max level... :P
As for the heroes, I think Onion knight is the most annoying one... he is so fast >=( ...Poor Exdeath, he has to be envious of Onion Knight fast moves xD...