Sweet mother of Jesus, finally got Ultimate Battler
Doomsday IS the way to go. I used the jump in Down+A and then A, A. I kept applying pressure so I could force the AI to clash as soon as possible, better for them to get some health back than me being caught up in a random super move
Overall for me Sinestro and Superman were the worst of the bunch, Im so glad its over! Godspeed to everybody still working on it and keep at it guys cuz this will be a very liberating achievement!