The 64 Demon/Devil Kings in Might and Magic 2.
The game is already happy to drop 1000+ enemies that are insanely powerful on you. By the time you reach the final area, you probably already have a level 30+ team who's more than capable of finishing things off. Tons of health, good stats, all the spells, and some quality gear. Right before the final fight, you meet the 64 Kings who bow to your accomplishments. You have the option of moving past them, or fighting them. If you choose to fight them, all the stuff you have so far won't be enough to take down 10 of them before your entire team is wiped.
If you want to even attempt to take down the 64 Kings, you need to get serious about boosting your stats to their maximum(254 in everything except ENDurance which will actually loop back around and be less than having 160), leveling up to push your attack and HP through the roof(level 60-70 or higher), and you'll need to figure out a way to grind up the gold and EXP needed to do both BEFORE your characters age up far enough to start losing effectiveness. Grinding up some +gear up to +30 to +60 is also helpful. Even then, you need to wipe them FAST because they do AoE attacks that Eradicate party members, requiring two spells to bring them back that can and do fail often.
I've never beaten them legit, and only managed to clear all 64 with a heavily cheated party that had perfect stats and all +63 gear as well as being level 90.