Ethics Of Our Fathers
My Rebbe, HaGaon Rav Henoch Leibowitz, zt’l, would commonly say that the most powerful mussar lessons come directly from Chazal themselves.
Mussar
Seeing What You Want to See in the Gemara
How people with an agenda deny obvious truth and grasp at small inconsistencies, as shown by Pharaoh's astrologers and the Egyptian slaves.