The epitome of crap teachers for me was Mrs. B, my science and math teacher in grade 5. (The B does not stand for the obvious.)
One time we were writing notes in Science. I wrote down a couple pages, but I used a few contractions and shortened some parts of the notes. All the discussed ideas were still there, they were completely legible, and were I to use them to study off of I would have been just as fine had I copied and pasted them off a computer. Not enough for her; when she saw they weren't exactly the same, she kept me after school to rewrite them. Unsurprisingly, a huge part of the class was in the same boat as me.
In math, we had our own booklets with a good 40 pages or so of problems. Around 1/4 through, she announced that anyone who got lower than a certain mark would have to write the whole booklet, backwards (as in from question 80-or-whatever-it-was to 1), within a week. Note that we had started around a week, two weeks before that. I got below that mark. When I rechecked my work, though, I realized I did get the questions right, and I should have passed. When I tried to explain it to her, she tuned me out and refused to listen. I ended up having to do the whole booklet in a week. Somehow I managed to do it, though, and when I went back to doing the booklet afterward I still remembered some of the answers.
Also, my English teacher in grade 10 managed to lose our midterms, of all the tests she could possibly lose. She's not mean, though. She's a good teacher and all, but come on. Midterms.
Also my math teacher throughout literally all of junior high, because he was almost never there. We were having substitute teachers almost every other day by Grade 9.