Dugtrio

Dugtrio's ability Arena Trap is the main reason to use it in the first place, as it prevents grounded Pokemon from switching out, letting Dugtrio act as the most effective and reliable revenge killer for Ground teams. With a Focus Sash in conjunction with Arena Trap, Dugtrio can guarantee the removal of dangerous grounded threats like Choice Scarf Greninja locked into Ice Beam (or variants not carrying U-turn) and Excadrill. Dugtrio's reliability in disposing of specific threats for Ground teams is one of its greatest assets. In addition to sporting a fantastic ability, Dugtrio has a nice, uncrowded Speed tier that lets it outspeed troublesome grounded foes like Choice Specs Keldeo. Having access to Sucker Punch, Dugtrio can check faster and weakened threats in addition to some Psychic- and Ghost-types, the latter of which cannot be trapped, while preserving its Focus Sash. Furthermore, despite its atrocious Special Attack, Dugtrio actually becomes one the best checks to Tapu Bulu, Ground's greatest threat, with Sludge Wave. With Gravity support, Dugtrio can even trap and eliminate numerous airborne threats like Mega Charizard Y, Celesteela, and Zapdos. While Dugtrio's horrible defensive stats let it activate its Focus Sash and boost Reversal's Base Power to 200 more easily, they also make it really vulnerable to opposing revenge killers and let it easily fall prey to weaker moves and priority attacks. Dugtrio needs considerable team support in order to properly function; due to its frailty, it needs a safe way to enter the field, be it with a double switch, after a teammate's U-turn, or after a teammate has been KOed. Dugtrio also needs entry hazard control to keep its Focus Sash intact, or else it won't be able to properly fulfill its purpose of trapping and removing opposing threats. Without the help of Gravity, Dugtrio becomes near-useless against airborne threats, as it cannot seriously harm them with any of its moves. Finally, even though Dugtrio's Attack stat isn't that bad, it's not that great either, so opposing Pokemon need more often than not to be weakened before Dugtrio can properly revenge kill them. It's also too weak to seriously threaten most walls.