Here's her story- she's a 2 coming 3 year old Arab mare, has been kept in a paddock with other horses and does fine with them, but otherwise hasn't been handled since she was a weanling. She has very stallion-like behavior. She is very herdbound and will pace herself into a massive lather when stalled away from the rest of the horses. She rears, strikes, bites, kicks and will rush repeatedly. She is a spooky (spooks easily) mess to boot.
I have been working with her for a month and she has learned to lead, tie etc. She took a chunk out of the calf of the last trainer that worked with her. The first week we worked just on leading and space. She was very aggressive the first week. For the past 3 weeks she has been cooperative and willing, yesterday she had an aggressive outburst that was the worst I have seen. She didn't spin and try to kick me, but with a hairpin trigger will rush and strike and continue to do so. I haven't seen a horse in such a rage in a long time. I specialize in severe abuse cases and rescues, but she has no tell when she's snaps. I've never encountered a horse that doesn't portray in even the slightest way that there is about to be an attack.
I work with both of her siblings, (weanling and coming 2 year old) both of them are cooperative and have none of the same traits.