What was one thing your teacher did that you still can't forgive them for?

4th year in college in a 3rd world country. Final exams. Last exam. About to graduate after an agonizing year of microbiology. I don't remember exactly what I did, but he saw me and thought I was cheating off of another student. I was not. Starts yelling at me. I start yelling back. Fails me on the last test on the very very very last day of the last year of college and I was about to go on with my life. I had to repeat the whole year because of him. College is different in my country. You fail one class, you fail the whole year. I still hate him to this day. When he dies, I'll go shit on his grave.