Well, the worst was one who enjoyed failiing people, so would set tests that were really hard to pass. And then he would do things like mark you wrong on things you got right just to make sure you got a fail.
One had a habit of telling you your draft work was great and then failing you on the final copy. She did that to a couple of students I know on a compulsory project for a compulsory VCE subject that meant they had to repeat Year 12. I had her for Year 11 psychology, a subject which was not offered until enough students lobbied for it that they changed the curriculum. Over half that enthusiastic class dropped it after the first semester with her teaching.
Some of it was just general contempt for us as people - like making us stay out in the rain during class breaks because they didn’t want the hassle of declaring it a “wet day” which allowed us to use classrooms on breaks.
Some were just incompetent, like the accounting teacher that could only set work from the book and mark it against a scoring guide but didn’t actually understand the material in the slightest.
The best teachers I had were what I would consider should be the minimum standard - they taught coherently and didn’t seem to actually hate the students.
That was always so painful. Enduring extreme boredom was however the most useful skill I learned in school. I suspect I would have been better served by learning to actively work to achieve things instead, but that was generally discouraged.