If you refer to someone as another person's henchman, you mean that they work for or support the other person, especially by doing unpleasant, violent, or dishonest things on their behalf.
英汉词典释义
n.
<贬>心腹,党羽,喽啰
The gang chief went everywhere accompanied by his henchman.那流氓头子到什么地方都有手下的狗腿子跟着。He thrived on the adulation of his henchmen.他是靠下属的奉承而发迹的。