OKW has the best non-doctrinal tank destroyer in the game. The JagdPanzer is amazing when handled well. Unfortunately, entitled players have gotten use to the King Tiger and JagdTiger ease of use.
Best is very opinionated, I think it's kinda crap. I'd rather use an SU-85 or hell, even a StuG, at least I can rely on that to hit and it doesn't need babysat 100% of the time due to some weird LOS handicap that out of every unit in the game, only it suffers. At least the SU-85 has better accuracy, penetration, and can spot for itself, while the StuG is cheaper and can get Spotting Scopes. Meanwhile someone forgot to tell the Jagdpanzer crew to watch their backside.