I don't mind how it's done without magic. But we were the ones who chose limited support magic items only. A magical enslavement collar is way beyond that.
And to use your SAO example, notice that red players were hunted and imprisoned regularly if people didn't outright kill them in retaliation for the crimes they committed. The fact that people will die doesn't mean that people will treat it differently.
If you kill them in the game you kill them for real that makes you a very real murderer the fact that it's going to happen doesn't change that. People will die every day for real doesn't mean murder is ok it's no different in the game.
More of my characters are more the criminal types then good types, my initial background for this character was a criminal type so that she could just ignore any crimes you guys commit but since that one was rejected I swapped to using this one and this one is based off me.
If I knew you were enslaving or killing or stealing from people for real then I would turn you in, so my character in the game will do the same.
My plan was to capture the animal myself in a humane manner, feed it, care for it, take it out on hunting trips with me and generally bond with it over time to tame it. You could beat an animal into obedience that would be a much quicker solution if you don't want to tame it or buy an animal thats bean beaten into obedience then it'll obey anyone but then it won't be loyal and if it sees the chance it'll go for your throat.
But you can't buy an animal thats tame and have it be tame for you, it's tame for it's tamer not for a random guy it's never met for you at best it would be wary and borderline disobedient. Taming a wild animal into a willing partner isn't mean to be quick or easy.