Assuming that garchomp has a move for Skarmory,
The only way to kill him is by sacrificing one pokemon to inflict ""chip damage""" and revege kill with something with more speed, and there is only 6 in OU :
Dugtrio, Infernape, Mienshao, Gengar, Jolteon, Starmie.
If you add the fact that Garchomp has a Yachee berry, the damage outputs are still inconclusive:
252 SpA Choice Specs Starmie Ice Beam vs. 0 HP / 4 SpD Yache Berry Garchomp: 146-174 (79.7 - 95%) -- guaranteed 2HKO
252 SpA Choice Specs Starmie Surf vs. 0 HP / 4 SpD Garchomp: 109-130 (59.5 - 71%) -- guaranteed 2HKO
252 SpA Choice Specs Gengar Hidden Power Ice vs. 0 HP / 4 SpD Yache Berry Garchomp: 116-138 (63.3 - 75.4%) -- guaranteed 2HKO
252 SpA Choice Specs Gengar Shadow Ball vs. 0 HP / 4 SpD Garchomp: 117-138 (63.9 - 75.4%) -- guaranteed 2HKO
252 Atk Choice Band Mienshao High Jump Kick vs. 0 HP / 0 Def Garchomp: 169-199 (92.3 - 108.7%) -- 56.3% chance to OHKO (NICE CB DUDE)
252 SpA Choice Specs Jolteon Hidden Power Ice vs. 0 HP / 4 SpD Yache Berry Garchomp: 104-124 (56.8 - 67.7%) -- guaranteed 2HKO
252 Atk Choice Band Infernape Close Combat vs. 0 HP / 0 Def Garchomp: 138-163 (75.4 - 89%) -- guaranteed 2HKO
And at least, 90-95% scarfed mons are useless versus him, even with some chip damage.