Captain America Double Duty

Boost Cap's attack to 3 with Combat Training and 4 with Aggressive Conditioning. With two Fluid Motion on the table, you can play cheap attack events like Clobber and One by One to get him up to 6. Then use Cap's "I Can Do this All Day" ability to get double duty out of that bonus and swing for 12 in one phase.

That takes a lot of setup and the stars need to align. But realistically, this is a deck which will see Cap attack twice for at least 4 per swing reliably. Cap will need thwart and defend as the board state requires, but allies in the deck round out your ability to thwart, attack, and to defend in order to free Cap up to do his attacks.

Jarnbjorn is in the deck simply because it synergizes so well with Cap, but it's not a part of the core strategy here.

Against standard Klaw I had the combo up and running pretty well, swinging for 5 twice a round in the late game.

I played a game against Civil War's Iron Man (standard) with a bunch of Tech mod sets (Goblin Gear, Osborn Tech but I ignored their Surge keyword, and Military Grade) and won handily, but the attack boosts for Cap did not come online. When the villain/leader deck requires you to spend a bunch of extra resources like Iron Man does, the deck can handle it fine but may not have the flexibility to play wishlist cards like Fluid Motion.