Tie between Cilan and Lenora. With Cilan it was hard because I did not train my Pansear because I did not know about Audino training at the time and it took soooooooo long just battling lillipups, patrats, and purloins and Lenora's Retaliate got me because my Dewott had a nature that hurt it speed and it was slow and got KO'd. Had to win on a VERY lucky Critical Hit from pansear. The rest were pretty easy, Iris's gym was tough getting through with all the trainers but she herself was easy. Clay and Brycen were the easiest, I KO'd all of their pokes with one pokemon.