for vanguards/tanks:

adam is perfect for the role, he'd be a brawler tank who has an option to fly and in turn you use your holy light while on the ground you use your axe, for an ultimate he would shoot a massive beam of holy light similair to iron man's maximum pulse

mammon he would play similair to magneto where you shield your team and I can imagine him having a life steal type thing to go with the greed theme, for an ultimate he could enter his demonic form

satan he would play similair to wolverine where the more damage you deal the higher your rage meter goes, his ultimate would be shooting fire or something idk

loona would be a dive tank similair to venom or captain america and her ultimate may be similar to black panther

carmilla who would play similair to rogue and be a brawler and for her ultimate her daughters come in to help her

ozzie and he would play similair to peni parker being more made for crowd control and his ultimate he enters his demonic form

bee would be a flying tank similair to angela and she would grab people and throw them off the map, her ultimate would be to lay down a bunch of honey and shit to stick the enemy team so her and her team to do damage to her

for duelists/dps:

vaggie would fit really well here, she would play similair to wolverine and be a tank buster using her spear and for her ultimate she could gain her wings and fly around

lute would be a good counter pick for vaggie and have less health but deal more damage for her ultimate she enters and enraged state and gravity plays

vox would be a dive character who uses his teleportation to shred through support health (you'll see why later ;), for an ultimate I can see him entering his demonic form

niffty would also be a dive character playing similair to black panther and for an ultimate she gains a speed boost and health boost similair to captain america

lucifer would be a dps who takes a lot of skill to play and is fast but once you get his combos down he is super effective similair to spider man, for his ultimate a giant fireball similair to fear magneto in rivals

blitz who would play similair to bucky mostly using his pistol, for his ultimate he could pull out a big rocket launcher or something

millie would be a dive character who would use her axe to shred through health and her ultimate would be similair to thor's

husk and he would play similair to gambit but a dps, his ultimate would be him blowing up some dice similair to what he did to val

angel would play similair to punisher with his guns and for his ultimate he would pull out more guns

for supports/ strategists:

alastor I know its a shock but think about it, alastor's main weapon is his cunning, he beats his opponents mentally first then physically so making him a support to distract the enemy team would be perfect have him play similair to cloak where he blinds them and for his ultimate he enters his demonic form and it boosts everyone else

baxter uses his tech and creatures to confuse the enemy and heal the team for an ultimatr he pulls out that four legged fish thing from his flashback and it fights for him plus he compliments niffty's dps

pentious and he'd use his inventions to heal the team and his ultimate would be his blimp thing shooting a massive laser

for charlie I see her as a strategist and she heals her team via her music powers, her ultimate is her demonic form

moxxie would be a dps, support hybrid who would mostly use his sniper but also have some moves to help his team out, his ult would be to encourage everyone else making them do more damage

velvette would use her magic to support everyone else and heal people and her ultimate would be some big ass spell

  
valentino would heal via his smoke and his ultimate would be him flying around and shooting everyone like star lord

building a hazbin hero shooter roster similair to marvel rivals