Keep in mind that I am not referring to based on the moveset, I'm referring to based on the Pokémon the gym leader has.
Whether it being uncreative, weak or too easy. All these factors can make for a bad Pokémon team.
As for me, the one I'm going with is Morty.
He only has Pokémon from the same evolutionary line, that's lazy. Falkner does it as well, but that's more excusable since he is the first gym leader in the game. But seriously, why couldn't Morty have a Misdreavus?
That's one of the biggest problems I have with Gen II, only half of the gym leaders have a Pokémon introduced in that generation. I understand options were limited back then, but that doesn't excuse it. There was at least one non-legendary Pokémon of each type back then. They could have easily given all the gym leaders at least one johto Pokémon.
Thank goodness that got changed in later generations. In fact Wattson is literally the only gym leader after Gen II that didn't have a Pokémon from his generation the first game he was in.