My Soul to Take

After giving up his Soul, Frisk and Chara develops a partnership with each other. Before completing their sixth Genocide run, Chara tells Frisk that she grows tired of doing the same thing over again. After sparing Sans, he warns the two that if they gain a single point of EXP, there'd be hell to pay. Can the two do a successful Pacifist run, or will they go back to their old ways?