I know, I've spent hundreds of hours playing Disgaea. It was an experience.
oddly enough, a level 9999 enemy creature isn't that strong. Levels ARE important, but the game mechanics dictate that the stats you receive from leveling aren't even 1/10 as important as the stat boosts you get from having excellent equipment, and random lvl 9999 monsters usually don't have good equipment.
Although, acquiring said 'excellent' equipment is a fucking epic adventure, because of how the equipment system is set up. (I WILL elaborate if anyone's curious)
Oddly enough...
the strongest enemy in the game is a single monster, Uber Prinny Baal, that has truly absurd stats, AWESOME equipment, and devastating special attacks. Numerical superiority is a must, or you'll never win. ever.
Funny thing though? Their is a skill that lets you randomly change special properties attached to the playing field, and using this gives you a rough 10-15% chance of getting few "invincibility" panels. Place as many thieves as you can on these, and you can repeatedly attempt to steal his equipment because of how stealing mechanics work. Once you do that, his stats are seriously crippled, and by abusing the invincibility panels even more, you can whittle his health down ever so slowly, guaranteeing a win with a very weak party.
It is only now that I realize I spent way too much fucking time playing that game. I know everything about it, by heart.
I've only played the first Disgaea, I'm too afraid I might get absorbed again if I play the sequals.