Is there helicopter adversary pilots? An aggressor squadron for helicopters?
Depends on what you mean. The guys in Fallon used to have a “Red Air” painted up HH-60H that was used in Air Wing Exercises and the Seahawk WTI Course. Not sure if they have a -60S with the same paint job. Either way, there’s regularly a “red air”/adversary helo in large force exercises, much to the consternation of many an RMC.
If you mean “dogfighting”, it’s referred to as helicopter dynamic maneuvering and is a taught skill set, but there aren’t a lot of chances to get your Nicholas Cage Firebirds routine on in practice.