So, I'm used to “rizz” meaning flirtability, which I guess would be up to the individual Onix..?
But since you seem to be asking if Onix is a good Pokémon, I hate to break it to you he's pretty bad.
Onix has Rock/Ground typing... Well, Ground being there is its saving grace, Rock sucks as a type, with all its common weaknesses and few offensive ability.
Furthermore, Onix has abysmal stats; it has really high Physical Defence but the same HP stat as a Hoppip and the same Special Defence stat as a Mareep; so zero survivability.
If it's not a tank, it could be a good sweeper, right? Well, it's got OK Speed, but the Attack stat of a fucking Budew!
If it's supposed to get rizz points for defeating a first-out-of-three stages Pokémon and only with type advantage, then that really shows it's bad.
Sorry harlyson, I agree with the chat that Onix's got no rizz.