I suppose he’s the only one that’s on his own. The goons in Paris are together depending on which district they are in, meanwhile Skarsgard’s men just want Wick dead and therefore don’t want to hurt the other people trying to kill Wick. It stands to reason that since he is neither part of the gangs in Paris, nor one the high table men then he would have to keep John alive until he himself can kill him.

So that they didn’t kill John Wick instead of him killing John Wick? The only reason he didn’t kill him was because John saved his dog.

He killed the other assassins in order to keep John alive so he could collect the reward later. I think the major reason that he changed sides is that after John shot the guy who was gonna kill the dog, Mr Nobody figured that the bodyguard guy and Skarsgard’s character was worse and he didn’t want to work for them. He also felt a debt to John. Also, while honor is a huge thing in the John Wick world, it seems to me that most of the big characters seem to stray away from honor, John himself among them.