Often times we work with a horse and we are told about things in their past that might not be good. So how do you train a horse that has been beaten, neglected, etc.? The same as you would train a horse that has had no training at all.
Don't put a label on a horse, they live in the moment, they dont live in the past. Dont train them expecting them to kick, bite, run away, etc. Get a thought and a purpose in your head of what you are going to do with that horse at that moment and then ask the horse to do it.
If you think of their past and what you expect they will do when you ask them to do something, it comes through in your feel and your body language. A horse can feel that also. Instead think about what you are asking the horse to do and set up your body and just ask. You might be surprised at what the horse has to offer.
An example is an owner leaded a horse. In the past this young horse would run, buck, rear, strike and intimidate the person leading it. The person leading the horse would walk in fear, sending the horse a message that there were things to fear so it better act on its instinct and also be fearful. The owner of the horse was asked to walk right out with the thought that this horse was going to walk/follow as any well trained horse, and walk with confidence. The owner did this and the horse followed like any well trained horse.
The horse will partner with the person who is doing the asking, they dont partner with the memories of the past, they live in the moment.