I've done so many evil things to my hair! Perms, bleach (double process!), heat styling and teasing (I went to high school in the 80s. In Texas.)
A lot of it was when I was too young to know better, but when I was an adult, the worst stuff I did was bleach related. I like the way I look blonde, but my hair just can't take it.
Oh, and that time I wanted locs and used the "twist and rip" method. It's just as bad as it sounds. That was probably the worst because there was so much breakage.