Overall worst experience involving a horse?

The last two, are about my TB mare Roxy. She is a big 16.1 hand mare, long spindly legs, race bred, lots of athleticism, and power. When I first got her she was pretty good, but I had a trainer at the time that was not the best, and so my horse started to have issues because the trainer would tell me to do stuff to bring her back in line that never worked, and she couldn't get on my mare to help me out at all, so my mare started getting a temper. She started having moments of bucking and rearing, and getting all pissy if I tried to slow her down going into a fence, as we were only jumping like 3 feet, and she had been jumping grand Prix with the trainer her previous owner had. When she bucks, she honestly could pass off as a bucking bronco. She had the twists, the turns, the locked legs, the head in the dirt, and all that jazz, which repeatedly hurt my back, and one day, in the middle of the bucking, she decided to go up in the air. And I mean seriously vertical to the ground. Everybody had already stopped and dismounted (this was during a lesson), and I can still see the look of horror on their faces as she went up. I honestly don't know how she didn't go over backwards, but I rode her around the arena a couple more times, made sure she knew it was wrong, and that she was good so we could end on a good note, and I was shaking like a leaf when I got off.

This one is the last one I promise. Same TB as above. The vet had just given me the okay to ride her again after a week off for a pulled tendon, and she decided after a bit of being fine, that she wanted to run, and so she managed to take off for a total of 3 strides before she stopped, and I didn't think much of it, continued walking and trotting her around, and then cooled her off and put her away. Nothing was wrong, or out of the ordinary. When I got there the next day, I went to get her out and the horse that had never been sore in almost 3 years, even when she had an infected puncture wound on her hind leg, couldn't walk. I finally got her to my tack shed, where I proceeded to call my dad, and the vet. By the time the vet got there, I had gotten her over to the concrete where the power is and the vets do their stuff, and my vet leaned his head out the window and told me to walk her toward the truck. After 3 steps he yelled at me to not move her, and asked if I had another horse I could ride for 6 months. He got out of his truck, walked over, and said "I can tell you right now, she has torn her tendon, but we are still going to do the whole ultrasound, and stuff to make sure", lo and behold, the ultra sound showed that her superficial flexor tendon was hanging by a thread. She was in so much pain that he didn't even need to sedate her to do the ultra sound like he does every other horse. He put a gel cast on her leg, then a pressure wrap over the gel cast, and told me he didn't want her moved at all for a week, and that there was a distinct possibility that she would never be sound again, and that I might want to look into breeding her, as i had talked about with him before. 6 months, 3 ultra sounds, 2 sedations, and numerous calls to talk with the vet later, she was perfectly fine with the exception of never being allowed to go faster than a good canter, never ridden in deep sand, and never turned out. And no quarantees that she would be okay jumping (which she was fine, jumped her over 5' courses right before I sold her).

When we first got Tanner and Magic, the people told us out right that they hadn't been ridden in five years. I automatically dubbed them "greenbroke until proven otherwise" and allowed no one but myself and my uncle who has broke horses before on them.
Since we bought them from the owners of the equestrian campground we were staying at, I had the chance to take them out for a ride right after we got them and did so, having no major problems (just a bit of reluctance to go, and little things like that.). When my mom (not an avid horse back rider) and my dad (who can ride, but can't be trusted with a sensitive horse) decided they wanted to ride, too, I put mom on the calmer, most responsive of the two (Magic) and dad on Ruby, while I rode Tanner and my uncle and his daughter rode on their sort-of green horses.
We had no problems whatsoever until we came to a small ditch with a creek running through it. Tanner crossed with no problem when I tested her, then I turned back to cross again and lead mom and Magic through the flatter, water-less crossing (in case Magic got upset). However, my uncle told mom to go through anyway, and Magic decided to sort of hop over the water. Mom rode through the jump, then fell off in the hard dirt. Magic spooked and ran for Tanner, kicking my mom in the ribs as she went. My dad jumped off Ruby and ran to my mom, and for whatever reason decided to take Ruby with him. She was all nervous and upset, and ended up hopping over the water, too. My dad yelled at her, scaring her more, and she bolted to where Magic and Tanner were, clipping my mom in the face with a hoof.
My mom broke a rib, dislocated another rib, and twisted her ankle. I still blame myself for listening to my uncle and letting her on Magic, and she hasn't ridden since, though she recently expressed an interest in riding Ruby sometime.

There are other stories I could tell, but that's by far the worst.

My absolute worst would have to be putting down lady...she wasnt even mine but my best friends...still i had been riding her for years and litterally learned to ride on her...we had spent so much time trying to save her too. She had coliced and even though she was small it took three of us to hold her an keep her from rolling. We walked her for three hours starting at six thirty in the morning until the vet arrived...my friends parents were cheap an would call in an emergancy vet because they didnt want to pay the extra money... She recovered from the colic but foundered a week later...then that coupled with her poor living conditions (wont go into this) did her in...we had her put down about three weeks later...

It was the worst day of my life....

The worst day of my life was when I went down to see Oscar and he was acting oddly in the field, trotting around which he never does! I thought something had just spooked him so I took him in anyway coz I was going 2 ride him. I put him in the stable and went to wash his bit. I came back 10 minutes later and he was looking odd. His ears were slightly back and every few minutes he'd throw his head a bit. I went iin and checked there were no flies and there wasn't. I called the stable hand down to see what she thought. I already knew he had colic but I wanted her to say it was something else. She said he was just messing about but I knew he wasn't. I ran down the yard to the instructor. she came down to see him and my heart sunk as Oscar tried to get down to roll! I ran in to get him up but she stopped me and said not to! He got half way down and suddenly he jumped back up. I took him out of the stable and kept him walking. I walked him around for 2 hours talking to him non stop. I was in autopilot mode. finally the vet came and I put oscar into the stable. The vet asked me the words I was dreading to hear " Has he got medical insurance" I crumpled because he didnt have them. He said he was possibly going 2 need an operation but the next 2 hours would tell his future. It cost at least 4000euro for an operation so he would have to be put down if he needed it. I was told to lunge him just walk with short bursts of trot to try let out all the gas trapped in his gut. I broke down seeing him the way he was.
Eventually he stopped sweating and seemed perkier. We called the vet back and he said he was lucky. That was by far the worst day of my life

The worst experience I have had yet and which still brings a pang of anger to my heart:
I used to work for this stupid woman who bred appys. She really liked breeding father to daughter and stuff like that in order to get colour. I don't know if this is acceptable in the breeder community (I know next to nothing about breeding or genetics) but I certainly hope not. Anyway her horses were all...messed up. Man, I can't even tell you. Then she had to euthanise this little week-old foal because it was so heavily inbred it had a multitude of problems, the least of which was the fact that its skin was sloughing off its legs. I listened to the vet berate this woman but did she listen? Hell I remember when he was born she was boasting at how beautiful this baby was, how he was even more colourful than his mom, blahblahblah.
Yeah, I left in disgust. Learned later that this wasn't the first time something like this has happened. Some people should not be allowed to own horses...or any other animals period. Let alone breed them so ******* irresponsibly. So much suffering just for greed.