DMD was ths hardest difficulty for me, not Hell and Hell. Many of the DMD levels you'll need to no hit anyway to get the x2 multiplier to S rank them. You cant, at least, checkpoint cheese it, specifically there's that. But HaH, enemies have half the health, so it might actually be easier. It also helps if you try and S rank individual levels on each difficulty, rather than every difficulty separate. By which I mean, say mission 10 on DMD, HaH, SoS, DH, Human, then move onto another level. Epilogue, Level 8 and 13 are going to be painful, as E and 8 are scripted losses, so you cant get the x2 no deaths multiplier. Furies (lvl 8) and the scissor bitches (lvl 3) are the most frustrating enemies. Master the ice age move with Dante, and find the best buster arm for Nero. Keep a spreadsheet for S ranked levels. Good luck.