1. by simply killing its counters? the panther is op cause it outclasses heavy tanks and tank destroyers alike for the cheap cost of 490 mp and 175 fuel(heavy tanks cost much more),and its non doctrinal and its not limited and has a pop of 16,thats OP.
2. the su-76 on the otherhand is not,tell me is it op to have a frigale tank destroyers that does 120 damage??
not thats not OP its a unit that you must bring in numbers to make it effective,by reducing its penetrattion you make it useless against tanks and punish the soviet player for making them.
3. the tiger ace was op cause it outclassed the tiger 1(came at the same time but didnt cost fuel only mp and was already at max vet)
the old flamehalftruck instawiped infantry and by the time it arrived there was no counter to it so it was OP
1. Outclasses its counters? It's a tank hunter that costs a significant amount of fuel more than other TDs. It's not meant to be countered by tanks (although SU-85s/Jacksons can fight it just fine; not on their own though), just use ATGs, mines etc.
IS-2s can fight Panthers and have way better AI. I don't know what your problem is.
2. Did I say that its stats were the problem? No, but it's too effective for its cost.
3. Those units did what they were meant to do. So they were fine by your definition.