I’m currently thinking it’s Immortal Hulk with the Hulk relic.
Relic allows you to chain 2 SP2’s; my 6 star Rank 4 can kill ROL Winter Soldier in 44 seconds. No Boosts and class disadvantage.
If you think it’s someone else, let me know the quickest time you can kill ROL Winter Soldier in and also keep in mind the star/rank.
P.S. I made a guide on how the relic makes I-Hulk really good:
https://forums.playcontestofchampions.com/en/discussion/340509/immortal-hulk-with-relic-is-nuts#latest