Well, mine isn't what I would call 'abuse', as much as just plain ignorance and stupidity; something like what yours is...
My first year in college I met a family at the church I was attending; turned out they had a yearling Paint\Mustang colt who was out of control. They had bought him the prior year off of a feedlot; they got him back into condition, and he was well cared for, but they had NO clue how to train a young horse. They were of the mentality that "lets get one that our daughter can grow up with."
Well, when they found out that I trained horses as a 'side' when ever I could, they asked if I could come out and evaluate him. So I went out one night after prayer meeting, and yes, this boy was out of control.
He bit, he would kick, charge...anything to get "his" way. HE was in control. So after the owner stepped away from the gate (hadn't entered), I asked for a lead rope. I went stepped in the stall\run in and when he came at me, I flung the lead rope at his chest...he gave me a "what the???" type look, and backed off a few steps...he tried charging again, and I did the same...this time he went out the gate and into the paddock. We kept doing this 'dance' until he finally came up with a friendly curious posture. When I reached to rub his neck, he snaked his neck around to bite me, but I just raised me arm...he hit my elbow and decided he wouldn't try that again (at least for that night). When that was over, I was rubbing his neck and body all over, and when I got around to his right side, he tried to strike at me with his front foot...I flipped the lead rope at his chest again, and we started our 'dance' again...til he finally came up, friendly, and let me rub him all over. This was not a horse who was afraid of humans; on the contrary, he was so used to being the leader, that he had a hard time submitting to leadership. It took a long time for me to undo the damage.
Like I said, not necessarily 'abuse' in the terms most people think of, but if a person goes into horse ownership blindly, the horse will suffer, whether it's physically, or mentally. I wound up buying that horse from my friends, spent two years training him, and wound up selling him to some really good friends of mine.