Pretty much all of the IW uniforms make their non-uniformed counterparts 0 to hero.
At the top on would probably be Ironman, Thor, spidey, Capt America, and war machine.
After that, you could just pick your favorite IW characters and be satisfied with the results.
The only uni’s I would stay away from is cull obsidian, proxima, and groot.
This is considering if you don’t have any uniforms for those characters. Homecoming spidey and rag Thor are still very usable is most game modes, so they may not be so high on the list for you if you already have those unis. (They still improve the characters a ton though)