One-Hit Knockout Moves are moves that are guaranteed to wipe out the foe in one hit. Numerous Pokémon can learn them. A pre-requisite to the success of this move is that the attacker must be equal to or higher than the level of the opposing Pokémon.
List of One-Hit Knockout Moves
Fissure
Pokémon that can learn Fissure via Level-Up
Diglett, Dugtrio, Camerupt, Trapinch, Barboach, Whiscash, Groudon, Wormadam (Sandy Cloak), Hippopotas and Hippowdon.
Pokémon that can learn Fissure via Breeding
Lapras, Snorlax, Swinub, Piloswine, Phanpy, Donphan, Wailmer, Wailord, Torkoal, Spheal, Sealeo, Walrein, Shieldon, Bastiodon, Shellos, Gastrodon and Mamoswine.
Guillotine
Pokémon that can learn Guillotine via Level-Up
Krabby, Kingler, Pinsir, Gligar, Corphish, Crawdaunt, Gliscor, and Haxorus.
Horn Drill
Pokémon That Can learn Horn Drill via Level-Up
Nidoran, Nidorino, Rhyhorn, Rhydon, Goldeen, Seaking,Rhyperior, and Excadrill.
Pokémon that can learn Horn Drill via Breeding
Ponyta, Rapidash, Seel, Dewgong and Lapras.
Sheer Cold
Pokémon that can learn Sheer Cold via Level-Up
Dewgong, Lapras, Articuno, Glalie, Spheal, Sealeo, Walrein, Kyogre, Snover,Abomasnow, and Cryogonal.