Torterra (M) @ Choice Band
Trait: Overgrow
EVs: 252 Atk / 164 HP / 92 Spd
Adamant Nature
- Wood Hammer
- Earthquake
- Stone Edge
- Bullet Seed
I think Choice Band Torterra is a good partner, considering there are a lot of things Torterra can do to help Omastar. One of the biggest things Omastar is capable of setting up on is a Choiced Flare Blitz, and while Torterra isn't the best lure for Fire moves considering it has a STAB Earthquake, and incoming Flare Blitz from the likes of Entei still means that Omastar pretty much gets a free set-up opportunity. However, Torterra also fixes several issues that Omastar can have that may hinder its sweep. Many of its revenge killers are Electric-type Pokemon, such as Scarf Rotom and Manectric, but Torterra is completely immune to their STABs, meaning that they are incapable of trying to gain momentum, which gives Torterra a free turn to do whatever it wants to. Torterra also OHKOs the likes of Lanturn, Clefable, Jynx (although it can't switch in), Roselia, and Slowking, while 2HKOing Amoonguss (Omastar can do enough to finish it off in this case) and Uxie with the appropriate move, which therefore potentially wears down the opponent's Omastar check(s) enough so then Omastar can potentially blast through them mid/late-game without that many issues. Torterra also gets a free switch into Thunder Waves from some of the above Pokemon that may try to stop it in this way. The speed EVs are to outspeeds and destroy Lanturn.
Calcs vs Omastar checks:
252 Atk Choice Band Torterra (+Atk) Wood Hammer vs 248 HP/144 Def Slowking: 147.07% - 174.05% (Guaranteed OHKO)
252 Atk Choice Band Torterra (+Atk) Wood Hammer vs 0 HP/0 Def Jynx: 233.95% - 275.65% (Guaranteed lol)
252 Atk Choice Band Torterra (+Atk) Wood Hammer vs 252 HP/152 Def Uxie (+Def) : 51.98% - 61.3% (2 hits to KO)
252 Atk Choice Band Torterra (+Atk) Wood Hammer vs 252 HP/0 Def Clefable: 93.91% - 110.66% (62.5% chance to OHKO)
252 Atk Choice Band Torterra (+Atk) Wood Hammer vs 64 HP/192 Def Lanturn: 165.6% - 195.09% (Guaranteed OHKO)
252 Atk Choice Band Torterra (+Atk) Earthquake vs 252 HP/0 Def Eviolite Roselia: 97.7% - 115.46% (87.5% chance to OHKO)
252 Atk Choice Band Torterra (+Atk) Earthquake vs 252 HP/0 Def Amoonguss: 73.84% - 87.04% (2 hits to KO)
252 Atk Choice Band Torterra (+Atk) Earthquake vs 252 HP/252 Def Eviolite Ferroseed (+Def) : 41.44% - 49.32% (3 hits to KO) (Ferroseed can do nothing back to it)
252 Atk Choice Band Torterra (+Atk) Stone Edge vs 252 HP/0 Def Mandibuzz : 65.57% - 77.36% (2 hits to KO)
Also, turtle is cool :)