Justice League. The big expanded one with dozens of members. Really, Superman could easily destroy at least the first four circles before needing help.
The Avengers. Thor alone could romp through the first five circles of hell before breaking a sweat.
The combined might of Azeroth. Really, any one group (Alliance, Horde, the Aspects, the naga, and alllllllll the others) could just about do it. Except for murlocs. Murlocs would be part of the enemy, because I want them to suffer for existing.
Every legendary Pokemon plus the fully evolved starters plus a bunch of the other top-tier. If Arceus is the closest thing to a true deity in the Pokemon universe, then he would probably be more than enough by himself.
The bad-asses of One Piece. WAY too diverse and numerous to go into which ones would kick the most ass. I suppose the big three admirals, the Shichibukai and the Four Emperors are a good start.
Everyone in Dragonball Z. Except maybe Krillin, because he's the butt-monkey to end all butt-monkeys.
I could sit here all day thinking up examples of small groups of people that could annihilate Hell. But I won't.