Bang, Hakumen, Jin, Ragna, Tager Makoto, and Tsubaki are the easiest on pad, Tager's 360/720 is about the hardest thing out of these guys.
Arakune, Hazama, Taokaka and Noel are pretty hard to play on the pad, a lot of dashes, feints and canceling with them.
Litchi and Rachel are hard to play on the pad, a lot of dashing, multiple inputs in a very fast manner, negative edging and canceling with these two.
Carl is the hardest on the pad, you have to use TWO PEOPLE at the SAME TIME. That should speak for itself.