In Pokemon Go, each Pokemon has catch rate and escape rate as hidden value. These are associated with how easy each Pokemon to be captured.
Actual capture rate is considered as based on bass catch rate, trainer level, Pokemon's CP, the way to throw Pokeball.
Best Pokemon to beat Dragonite/Gyarados
Dragonite
Charmander nests and spawn locations
Gastly nests and spawn locations
Earthquake - Ground Move
Ekans nests and spawn locations