Rhydon was the first Pokemon ever designed, but that doesn't necessarily mean it is useful in Pokemon GO.
Introduced in Generation I, Rhydon is the evolved form of Rhyhorn. It was in Generation IV that Rhydon received the popularity many thought it deserved, but never achieved.
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That is because an evolved form came along, known as Rhyperior. Now, Rhyperior is an absolute wrecking ball in Pokemon GO battles, but can Rhydon stand alone without the evolution taking place?
Is Rhydon worth using in Pokemon GO?
Rhydon has as many resistances as it does weaknesses. It can withstand hits in Pokemon GO from Normal, Rock, Flying, Fire, Electric, and Poison-type Pokemon.
In terms of vulnerability, Rhydon takes mega damage from Water, Grass, Ground, Ice, Steel, and Fighting-type Pokemon. This makes it's matchups in PVP a bit risky, because trainers won't know what their Pokemon GO opponent will use.
Getting it out of the way now, Rhydon is not useful in Pokemon GO PVP. Trainers must evolve it into Rhyperior in order to get any sort of effectiveness out of it. That is just the way it goes.
In terms of PVE, such as battling in Raids and against Pokemon left in Gyms, Rhydon can do a decent job if its evolution isn't available just yet. Its moveset is pretty solid and diverse.
Its best moveset are the STAB moves Mud-Slap and Earthquake, but it can also learn Rock Smash as a Fast Attack. Charged Attacks can be Megahorn, Surf, and Stone Edge aside from Earthquake.
This gives Rhydon some versatility in Pokemon GO PVE encounters. If trainers have a high-powered Rhydon without the means of evolving it, it can do some serious damage against Pokemon that can't return the favor.
It will be easily dispatched if left in a Gym to defend or up against other trainers in the GO Battle League. Knowing what Pokemon Rhydon will fight if attacking a Gym or doing a Raid makes it a solid option, but only in those specific situations.
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