Hell I know a few. If you guys have ever played Amored Core 2 then you that Mathiaas is a fucking BITCH! Though he's not a boss. He'll shoot your mech down in LITERALLY a matter of seconds! Other hard-ass enemies would be from FFX. At the monster arena on the plains. Anyone who's played that knows what I'm talking about. I'm sorry , but Omega Weapon, although incredibly strong as it is, doesn't come close to what Ive fought in this arena. I'm almost certain that the producers of FFX designed these monsters to test the Break HP/Damage limits abilities. These things, most of them, have hit points well over 10 million, some even 15! I literally spent half and hour trying to beat one particular monster when only one of my characters had Break Damage Limit on. He was doing 99,999 dmg and it still took that long. Can you imagine trying to kill something that has that amount of life with 3 characters and your hitting it for only 9,999 at max all the time if your lucky? Do the math. One monster called the Earth Eater......Damn! Not only does he have a shit load of life, but it also does a double attack for at least 8000 on ALL 3 characters at once...twice! 16000 x 3 x 2 = death within 15 seconds of the battle, even with Break HP Limit ability. To this day I still haven't beaten it. And then there are the 3 or 4 monsters that cast Ultima after EVERY attack you make on them. That was bitch, but i managed to beat them...except one. Stupid imp monster. Anyway I've put my 2 cents in....plus a quarter more.