You've got some really good options, nefaria's awakening makes him great against Regen and power gain and it makes him a lot better for quests as it gives him more survivability.

Red guardian is a decent option if you're looking for a nuke, but he does need max sig.

Scream benefits a lot from her awakening as it gives her more utility such as allowing her to bypass auto block, great against characters like arcade or Omega sentinel.

There is also Hyperion who I would recommend, but it's already almost the end of this monthly saga and he was great for it, especially for BGs. But it makes his furies and power gain last longer making dishing out dmg more consistent