Not really, because of its type water and grass moves do 4x the normal damage against it. Plus its Hp is horrible and its speed best thing to do is evolve it to steelix.
Chat with our AI personalities
In Pokemon Yellow Onix does not evolve, it is a one stage Pokemon.
If you mean,, what onix evolves into,, it's steelix,, but the is no Pokemon that evolves into onix
Unfortunately, you can't get an Onix in Pokemon Emerald. To have your own Onix, you need to trade it from FireRed or LeafGreen. Hope I helped :)
You can only get an "onix" in Pokemon sapphire if you have a Pokemon version that has an onix then use a linking cable with other GBA to trade it and then you'll have an onix but "onix's" data can't be stored in your pokedex.NOTE:You can only trade with a Pokemon version that have the same region as your Sapphire has;HOENN REGION.
Please see the related link for info on the pokemon, Onix