Enfys: big hits and stun/daze nullify her ability. You don’t want turn meter reduction, so leave CLS rebels on the bench. Stuff like first order, Jedi, and Sith are good. Also toons that ignore protection like Mother Talzin and Sith assassin.
Pheonix: they only multi attack if they crit. Padme teams are good at avoiding crits. Start with CLS rebels to get the upper hand early. Use an AoE daze like Bo-Katan or Darth Maul to shut down counters multi attacks. GAS also prevents crits on out of turn attacks.
Steadfast retribution: By far the hardest to counter. I use NS since they can just keep reviving through the damage and have a lot of healing. Zealous ambition makes NS a force since Asajj, Daka, MT are all support. Padme also counters SR pretty well. Imp troopers can work against slower teams - you’re safe if they never take a turn to hit you. If you have him, SEE can solo any GAS or SR team you find pretty easily for 3* finish.
Hope some of that helps.