I think BOSS would be the best because her curses (especially the gun) are insane. I beat "x must die difficulty" with her doing a normal run and it was a cake walk. also the awakening difficulty was easy with her.

Thanks for the tip. On the fifth or so try I beat it. Just had to survive the early game and beat Chunks as soon as he appears. The Ghost is annoying but normally easily dodgeable since you oneshot most rooms.

I did this one with Fuji and enabled her curses for free Cordelia shops and her increased speed/ damage curse and it basically completely negated the curse where you drop money every time you get hit. Boss's explosions definitely help during the final final boss though.

literally just use boss because of her extremely broken curses

Either Boss with curses or Lydia with curses

I did it with Axel, the cursed version with his axes make a perma freeze with chucks (and any other enemy), so don't matter if he is in his different versions you will always kill him without taking damage.

I used Digby, his hammer is great and he gets free healing from combos as well.

I made the a guide on getting the achievement and I used Fuji for her Free items at shop since one of the curses negated the shop spawning less.

Boss and Axel are the next best choices since with their curses they become extremely powerful.

I prefer Fuji since her run relies less on luck plus her curse benefits negate a lot of others.

I got it with Lydia in two tries, with all of her curses as well as the 12 general ones.