Sefer Gedolos Hatzadikim (Chelek 2, Ois 51) relates a story that depicts how Rav Levi Yitzchok of Berditchov zy”a aroused people to do teshuva.
One year on Shabbos Teshuva, he delivered a drasha in the bais knesses and said, “There are two people in this generation who act on a level like Aharon Hakohen, and I am one of them. Therefore, if you do teshuva, that would be wonderful. But if you don’t, I will choose one of you to be the se’ir l’Azazel...”
Everyone there began to cry and they all did teshuva.