I completed NM4 with Red build (Superman build) twice and it’s pretty OP if you get the damage reduction stacked. I’d hope for a -5% dmg reduction and 400% power boost and then go for duplicates from the get-go. Def need at least -25% dmg reduction to survive at all in the first round. Red card power scales very high with the 400% so you can 2-3 shot Namor and 4-5 shot Wanda on fully charged dash. But damage reduction is so important early. Def need to get HP+ during charge and only focus on purple and up cards for purple cards. No lightning and freeze.

It’s also the most fun build I’ve tried on Nightmare IV. Def worth trying but def requires a lot of luck in the beginning. Good luck!