Nephenee's art is among the best in the game, in my opinion. All of HACCAN's work is gorgeous, but Nephenee really sticks out to me. The colors in particular are pleasing to the eye. Totally not my bias for the character, either. Definitely not.
Wada's Legendary Hector, LA!Lyn, and B!Roy are also amazing. I enjoy Wada's art in general, but those characters look incredible. I'm especially fond of Legendary Hector's special and injured art; they both seem to perfectly encapsulate the character.