I like to tailor my limits to the people I'm dealing with. But if I'm alone, it's all a matter of risk/reward.
As cliche as it sounds, I have a code of sorts. 'Right' is whatever helps me and if it will help me in the long run, whatever helps other people. So I don't go around turning people into pin cushions or the like. Wrong is what is detrimental to me or detrimental to those I like to have around.
More generally, I do not harm the defenseless. Animals, children until a certain age, the elderly past a certain age. I might not go out of my way for them(well, maybe for animals) but I'm not going to try and hurt them either. If this makes any sense, there's no obstacle to overcome there. I would just be exerting power over the powerless. It does nothing for me, and in some cases it disgusts me, because of how low it is. Torturing an animal, a child, someone's grandfather or grandmother is just tasteless and beneath me. It shows that the person doing it is just a petty tyrant, the kind of person who'd break something just so others couldn't have it. They have no ambition.
I much prefer to work someone over to the point that they'll want me to do what I do. Moving their "will not cross" line slightly and slightly further, edging them into a mindset conducive to my wants.