Easily Carol. Best 4 in the game and none of her competition (if you can call them that are in your poll. No Vulture, Peggy, Medusa, Iceman, etc. make this even more of a no-brainer.
As others have said I generally would base it on who you have the most covers for with only the rare exception. If you have no pending or all/several of those listed pending and tied then here’s my priorities list (highest on top).
EDIT: Also anyone below the line definitely don’t champ unless you’re trying to save a vine cover.
Depends on your iso situation. If you are in good shape, then yeah, definately carol. If you are spending as soon as you get then try to wait until you hit a 14th cover in any of them.
One more voice to say C4rol first, but I gotta speak up for Wasp. She and C4rol are BFFs. Those two and Medusa were my Sim team for several seasons. Wasp’s one-turn CD didn’t get the repeater tile treatment, so once it’s going you’ll get tile buffs every. single. turn. if you run her with C4rol. Plus AP steal. And it hits hard if it’s matched away.
Yes. He’s a one trick pony but that trick is so good that he is an essential 4* to have. That one trick has shifted the meta. Your life gets infinitely easier having him and he actually has use unboosted over other boosted 4* (which only few 4* can claim). And while all these top tier 4s are beasts boosted, Grocket boosted is cheat code level insane the way he can drop teams. I’m pretty sure him boosted can get faster clear times than even Carol or Vulture boosted.
Cloak & Dagger definitely second, those guys do nearly every thing (single target damage + special tile removal, AOE, Attack tile creation, spammable attack, AP generation - you might even use Cloak’s black if you have nothing else to do with it!)