Wouldn't reccomend a 4* for just one fight out of 20, waste of a slot. I used doc ok, who can solo fairly easily but I've heard some people used him to ramp up aegon, yeah you die but if it's from the rock shield you keep your combo
Also can use Gulk, quake, symb supreme or magik. All except quake should be 5* r5 to survive his initial damage