What one of my 4 or 5*'s should I upgrade

IRONMAN21

5*
Black Panther (Civil War), Mephisto, Man Thing, She Hulk ,Iron Fist or Cyclops (New Xavier School)

4*
Warlock, Venom The Duck, Superior Iron Man, Guillotine, Venom, Starlord, Hawkeye(Ronin), Mole Man, Falcon, Black Panther, Massacre, Spider Ham, Wasp, Cross Bones, Ebony Maw, Tigra, Punisher 2099, The Overseer, Night Crawler or Spider Gwen ?

GrassKnuckles

For 5*s Man Thing, and She Hulk are the only good ones

For 4*s Warlock, Mole Man, Tigra, Masacre, Venom and Spider Ham are some of my favorite champs