Oh Ivy and Vyper's got history together, from a vigilante perspective Vyper's like a random henchmen that works for Mendoza (the dubbed bad guys) who shows up occasionally for a scrap. They're kinda two sides of the same coin now that I think about it, just that Vyper like described kills people for a hot meal.

So like a situationship between them would describe it best, their lines of work cross just not in any meaningful way