I've actually had mostly good instructors for CS. Or at least mediocre. The worst teacher I had was actually my Algebra II teacher in high school. She taught by reading, word for word, from our textbook. She would copy the example problems from that chapter onto the whiteboard. And then give us the rest of class to work on homework. She was basically a Text-to-Speech program for our textbook.

We all joked that she was drunk and the one locked cabinet in her classroom contained liquor. A year after I had her class she was fired. For drinking on the job. The joke turned out to be 100% true and they actually did find alcohol in the locked cabinet.