Amazons can certainly have a personal vendetta against a person, sometimes for reasons not immediately apparent. Males are more prone to aggression than females. They also have extremely good memories, so if you happen to resemble someone who mistreated your amazon in the past, you may have extra work ahead of you! Do you know how old your amazon is BTW? Males between the ages of 4 up through their early teens are much more prone to extreme aggression fueled by hormones. Parrots not only go through puberty but it lasts several years before they begin mellowing out and establish an adult pattern of loosing their minds in the spring and being normal the rest of the year. If your bird is in that 'amazon teenager' phase, that could also be a BIG part of your problems. Females also go through puberty, though the aggression is not typically as bad with them.
Target training with a clicker is a good first step to test the waters and see how the bird responds, but be warned, it is not the infallible method of parrot training people make it out to be. It's most effective on already sweet little just weaned babies if you ask me. My BFA was a rescue and at the height of puberty and he would just bite the stick in half and do a death dance and/or come after me. He was not interested in any treat I had to offer at that time in his life (unless perhaps I was offering up fingers as treats). It wasn't until after he had already became a nicer bird through other efforts that he became much more amenable to such methods, though after he was already nice, I find no need to lead him around with a stick and find he learns just fine through observation/behavioral feedback. Also, having grown up around amazons and observing their interactions with each other, I don't believe in positive reinforcement only either. I prefer to interact with my bird in a more normal way, giving him behavioral feedback as we go, be it good or bad. Amazons most certainly correct a flock mate if they have done something wrong. Now, we shouldn't exactly be nipping or chasing our bird when they're bad, but IMO, a undesirable consequence (NEVER physical discipline) for a undesirable action teaches them just as much about how we expect them to behave as a reward for a desirable action. It is also wise in some areas to offer an alternative as well (such as when my bird was learning not to chew stuff like furniture, I'd push his beak away and say no, then offer a small foot toy and praise him for taking/playing with that. He now has a relatively good understanding of what kind of things he can and cannot chew). I personally found techniques to deal with unruly toddlers (modified for parrots), like a firm voice, counting down, time outs, distractions etc... more effective at helping him learn how to live in a domestic home than waving a stick in his face and clicking at him when he bit it in half or only praising him for good behavior, leaving what constituted unacceptable behavior up for interpretation. Thats just me though.
