Who should I rank up first?

I only have 4 stars of Masacre and Red Hulk for the Flaming Trinity, but I know Domino is still very solid without the synergy. I've started to get the play style of Venom the Duck down a lot better, but how you build up his RNA Bank is obviously very much reliant on RnG. So, I'm a bit torn on how I should take up next. My only 5 star currently at 4/55 is Captain Beardo.