Man, I've read up to around page 25.
Here are some of my characters.
Almost any boss I've fought in Devil May Cry.
The Weapons in FFVII (I only actually attempted Ruby once, and that was years ago, and I didn't even prepare for it, nor do I really care to beat them.)
Sephiroth in Kingdom Hearts - The problem with me and him is when he starts casting Sin Harvest, and I mis-time my attack, and instantly sends me down to critical.
One of the creatures from FFX's battle arena - he's the guy who has the attack convergance. He's one of the creatures that seriously annoyed me, besides the Jumbo Flan. That battle took awhile since I had to contantly switch people and heal and prepare for its attack.
Some Bosses that were mentioned but I beat/wasn't to happy with.
FFIX - This is going to sound odd, but I found Ozma to be a dissapointment. The thing is, after losing to him twice (without really preparing), I decided to go out of my way to prepare for him (lv to 99 and such). At around 70, I decided to see where I stand with him. I had Zidaine with Thievery at around 8000, Freya with a decent Dragon Lance, Aramant, and Vivi.
I beat him in 10 minutes, if that. He didn't cast curse once, and he used Meteor once (killed my party, but had auto live with auto-regan)
FFVIII - Omega Weapon. However, I did the Gllgamesh trick and used Squall, Zell, and Irvin. Here's the thing, I beat him at LEVEL 7 (Which means no Lionheart for me). (I beat the entire game without leveling up).
FFX - Nemesis/Omega God. After the struggle just to make it to him, he's a completely joke.
Skies of Arcadia - Rameriz final battle. ...It's a shame that he wasn't all that strong.
There are others, but till next time...