To get the trophy called “Bad Boss”, you must strike a follower enough times before he turns around and betrays you.
It’s really simple. First, dominate a captain or war chief and make them your bodyguard.
Next, I suggest finding an isolated spot where there are less or no enemies nearby, then summon your bodyguard. Once they appear, press
towards them, attacking them constantly until they lock weapons with you. Once they are done with their speech and you both back off from each other, the trophy should unlock.
Have fun and good luck!