Quoted By:
This guy, geodude and onix were easy, but his fucking cranidos outspeed most pokemon you can have at this point of the game so it will make you flinch nearly every turn with his headbutt. Add that to cranidos high attack stat and pursuit to finish a weakened pokemon when you switch.
If like me you hate grinding and didn't already have your starter evolved at this point, this guy is probably the hardest first gym leader in the whole franchise.