Generally speaking, what’s the shittiest type to exclusively limit yourself to catching and beat games with? (secondary types allowed i.e. you can have a ground/grass pokemon in your only grass party)

I always naturally assumed bugs would be the hardest to run with, but I absolutely cruised through Alpha Sapphire with an all-bug team. Then I tried only Electric Pokémon in Y which was somewhat harder but still nothing too crazy. But then I tried only Poison types in Alpha Sapphire and it was nigh-unbeatable without overleveling.