Hyperspeed Hellcat

Hellcat's ability doesn't seem that amazing on its face: she doesn't get to block if you're using it, so you've spent three resources for 2 ATK, 4 THW, or 1 ATK + 2 THW. Plus, after you've put her back in your hand, either you're spending most of that hand getting her back on the table, or you're just spending her as a resource.

Enter: the pile of Support cards in this deck. Mighty Avengers cranks up the value on Hellcat and the rest of your allies, and a steady supply of Quinjets will help her get back on the field. The big combo though is Avengers Tower + Helicarrier + Team-Building Exercise. Activate those three cards, with TBE last, and Hellcat pops right back into play for zero cards played. Now you can loop Hellcat, activating her twice every turn: use Hellcat, return to hand, play her back out, use a second time. Every turn, she generates 4 ATK, 6 THW, or 2 ATK + 3 THW. Plus whatever you can do with Jennifer and your entire hand of cards.

I like to keep a deck built for every hero, so I try not to "use up all the good cards" in any single deck. If you want to tweak this deck to be more powerful, probably cut the Moxies and maybe the Quinjets, add a second Mighty Avengers to find it faster, consider more Call for Aid to find Hellcat, and add more repeating resource/discount cards (Quincarrier, second TBE, second Helicarrier). You can also tweak the ally base (just make sure they're all Avengers).