What fish species would eat following species.pumkinseed sunfish,black bullhead catfish and prussian carp.

Flathead Catfish

you might wales catfish in your area? or Pike?

Are you near the coast?

LMB. Pumpkinseed and bullhead are very easy to trap, so if you're looking to reduce their numbers in a pond build yourself a nice cloverleaf trap or 5 lol

If my pond ever goes down the path of stunted, overpopulated fish...My fall back is flathead cats, but only as a last resort. I would think within a couple years the pond would have some serious fighting fish to be caught.

LMB of the medium to larger size would certainly help you out and if you could stock single sex LMB you would not have to worry about their overpopulation tendencies.