Hansel now…Gergorion if you get him for sure. Lianna Zeline and Alby are the only other worthwhile greens for 5*. Caedmon is pretty good too. Melendor for healer, possibly kasshrek.
In general when you’re looking for advice of this kind it’s helpful to share a few things: Heroes to choose from (you’ve done this), Ascension items available (to help choose between 4/5* hero ascensions), and Other heroes on your top team (to help suggest cooperative specials).
That said, this one’s pretty easy and I agree with everyone here. Hansel is the choice. Only consider Caedmon if you have no fast hitters on your team and already have Gretel or Merlin leveling or maxed.