I really hate whenever I try to explain how some bad rules can be abused and immediatelly get someone say shit like “If this happens in your group, change it” as if that would solve the problem. And whenever it is not soemthing you witnessed personally, then it means it never happens and could never happen.
It’s legit not hard to make an OP/powerful character in either VtM or CoC, assuming youre talking about making a character good at combat (which is usually what people talk about in this context with power gaming). I don’t play PF2e, though, so i cant speak there.
CoC take high dex, put 90+ in handguns, take the pulp talents rapid fire and quick draw, wear a bandolier of guns, and dual wield pistols that you fire 6 shots from per turn. If you dont care about going first, then fast load if you care about reloading, if not, then just take shadow and start combat hidden for two attacks with a bonus die at the start.
For VtM its easy as take fist of caine and lightning strike. If you aren’t playing as elders, this requires gaining some exp first. I know there’s other combos that i cant think of off hand that are pretty potent too.
Each of these do have counters in the form of monsters immune to guns (CoC), or celerity 5 opponents (VtM), but thats no different than a DM in D&D always throwing fireballs at the guy with high AC. It begins to be apparent when its happening all the time that the GM/DM/Keeper/whatever is specifically targeting your weakness.