Magneton because the champion is water
If you teach it good moves like thunderbolt
In my opioion I would use a fire fighting type Pokemon, I used Combusken's ember alot for most of the rock type Pokemon and then if that didn't work I would use the fighting moves Combusken has.
aggron
Magneton evolves into Magnezone.
Aggron is a steel type Pokemon
Magneton, as in to Magnezone, or from Magnemite to Magneton? Magneton evolves into Magnezone when he levels up in Mt. Coronet. Magnemite evolves at lvl 30
You can't catch aggron but you can catch a lairon at victory road to get aggron train Lairon to level 42.
Aggron is number 306 in the pokedex.
You have to migrate a lairon or Aggron from ruby once you have lairon you must get it to level 42 then it evolves same with Aggron.
Magneton from the first generation Fossil set is rare, as well as first generation Team Rocket dark magneton and Neo Revelation magneton.
level magneton in mt coronet.
Aggron is a Rock and Steel type pokemon.