Some bug pokémon have their weakness listed as 'Onix' on google search : r/ pokemon

Onix 138/264 Non Holo Common Fusion Strike Pokemon Card NM

Onix type, strengths, weaknesses, evolutions, moves, and stats - PokéStop.io

Ah yes, weak to onix : r/pokemon

Onix - 92/130 - Common - Reverse Holo - Pokemon Singles » Diamond and Pearl Sets » Diamond and Pearl - Spell Bound

Onix Unleashed, Pokémon

Onix, Paradox Rift, TCG Card Database

All Rock-type Pokémon weaknesses, explained - Dot Esports

Onix (bw9-61) - Pokémon Card Database - PokemonCard

Ah yes, Volcanion's weakness O N I X : r/pokemon

Pokemon Basic Common Card - Onix 56/102