The entire OU banlist can be found
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The Dugtrio+Truant Entrainment Durant strategy is gimmicky and wouldn't be successful against anyone who is reasonably good at this game. This is because Durant is extremely frail, meaning it has a hard time getting onto the field outside of after something has just fainted, and because there is a turn to switch out on the turn that you switch from Durant to Dugtrio, and it also doesn't account for the fact that even after 6 Hone Claws boosts Dugtrio's power is still very lacking in general, meaning that it often won't be able to clean up the entire opposing team. Usually you can achieve the goal of this with a more powerful Pokémon such as Landorus-T with a boosting move which allows for a very fast boost to it's stats (+2 in one turn), such as Swords Dance.