Oi, people, what's going on? We're slipping here.
Talonflame @ Choice Band
Jolly Nature
Gale Wings
-Brave Bird
-Flare Blitz
-U-turn
-Tailwind
Barring the fact you didn't list any EVs...
184 SpA Choice Specs Keldeo Hydro Pump vs. 4 HP / 0 SpD Talonflame: 692-816 (232.2 - 273.8%) -- guaranteed OHKO
184 SpA Choice Specs Keldeo Hydro Pump vs. 252 HP / 0 SpD Talonflame: 692-816 (192.2 - 226.6%) -- guaranteed OHKO
184 SpA Choice Specs Keldeo Hydro Pump vs. 252 HP / 252 SpD Talonflame: 510-600 (141.6 - 166.6%) -- guaranteed OHKO
Talonflame gets destroyed on the switch pretty much regardless.
But prior to that...
Keldeo @ Choice Specs
Timid Nature
Justified
252 HP / 72 Def / 184 Sp. Atk
-Hydro Pump
-Secret Sword
-Icy Wind
-HP Flying
Yeah I used THOSE EV's just to counter ScarfChomp
252+ Atk Garchomp Earthquake vs. 252 HP / 72 Def Keldeo: 181-214 (46.8 - 55.4%) -- 72.7% chance to 2HKO
Keldeo only wins about 28% of the time, since it eats an Earthquake on the switch and another due to Garchomp outspeeding (Scarf and all). So it doesn't actually counter ScarfChomp, so back to Chomp we go.
Mamoswine @ Choice Band
Adamant Nature
Thick Fat
252 HP / 252 Atk / 4 Def
-Ice Shard
-Stone Edge
-Earthquake
-Superpower
252+ Atk Garchomp Earthquake vs. 252 HP / 0 Def Mamoswine: 216-255 (50.9 - 60.1%) -- guaranteed 2HKO
252+ Atk Choice Band Mamoswine Ice Shard vs. 4 HP / 0 Def Garchomp: 448-532 (125.1 - 148.6%) -- guaranteed OHKO
Priority and whatnot.