If a person has got deep enmity for a bunch of individuals then either he will go alone and ambush everyone or will join those guys as it is said if you can’t beat them then just join them;
The guys have got no idea what is going to come at them as that individual is more than a spy, he will win trust of everyone by doing ‘n’ things for those people;
All of the guys would feel that he is one of them but after some time, he will Assasin everyone nicely not physically but mentally as he wanted nothing but revenge and to be honest it’s Vendetta