Use the Ms. Marvel Stun-Lock glitch to beat Ultimate Alliance mode. Then use the Alliance Enhancement reset glitch to max your stats. You will effectively be playing on "Story Mode" difficulty even on the hardest settings.

Dr. Doom requires you to beat the "Shadow of Doom" epilogue. However, pressing on the character select screen (while hovering over a locked Doom) unlocks his "Kang's Variant" costume early. This does not unlock the character, but gives you a level 1 jump-start costume with +2000 Vitality.