THE NEW THUNDERBOLTS
I say “New” Thunderbolts, because Civil War led to an almost completely new Thunderbolts team that was comprised of Marvel’s biggest supervillains. In the Marvel Cinematic Universe, that’s going to be more difficult to pull off since most of the villains tend to get killed off in their one and only appearance.
Of course, Venom and Lady Deathstrike wouldn’t be able to appear in Captain America: Civil War. But Bullseye, Songbird, Radioactive Man and Taskmaster would be easy to include. Plus, this would be a natural way to bring Frank Grillo back as Crossbones. The whole point of the Thunderbolts is that Tony Stark and the U.S. government were conscripting supervillains into their war against Cap and the unregistered superheroes.
After that, there really wasn’t much moral high ground for Iron Man and his followers.