Opinion on Mephisto?

Kerneas

Got him as 5* today. I heard he is useful w Synergies (Champion & Sym Supreme). How high should I rank him? And how useful is he?

Battle_Greninja

Mine is R3 and I use him occasionally with sym supreme and champion. He was my best champ after SS himself against last 2 Uncollected EQ boss
Nova and Silver surfer

Deadpool87

He's a really annoying war defender

Kalantak

not bad but not good either decent damage with SS/champion synergy but the champion guy is really bad so mephisto
- good for AQ with SS
- occationnaly a kill or two on AWd
- probably useful utility if some node requires u to bring poison immune,+ incinerate immune

ShrikeTzu

I use him with GR and SS in AQ some times, he does decent damage and you can use him for a lot of fights in a row because of his stacking souls... he can take a lot of damage and heal on up to 90% and carry on his merry way. His poison immunity is useful for some paths in AQ. He isnt going to change your life... I haven't used him at all in varient for anything yet... but I dont regret having him as an r4 5 star at all. He is a decent defender but he has been out so long that it's hard to place him because of Diversity. He is very useful against cosmic bosses in event quests, because his buff lock mechanic doesn't depend on RNG or doing a combo... it's just on for a while at the start.

dot_ditto

My 5* R4 Mephisto is my go to for handling pesky champs like:

Hyperion (stops his power gain)
Annihilus (stops his unstoppable)
Medusa (prevents fury, hence prevents autoblock)
Vision Aarkus (prevents power gain)

.. etc.

Maybe not the best for that .. but it's the best option got . and it works quite well!