Best character introduced in the prequels?
Best introduced in Force Awakens?
Best introduced in Rogue One?
Prequels: Palpatine. If we count Clone Wars, Ahsoka Tano
Force Awakens: Kylo Ren (yes he can be a whiny emo, but he has more depth than most of the others), Poe Dameron
Rogue One: Chirrut 100%, followed by K2SO and Cassian