Beat elite 4 easily with swampert
Make sure swampert has these moves (surf return and ice beam and one move of your choice) i did this with a level 100 swampert but it might work wtih a lower level swampert also needs to like you alot because of return use these attacks for these types
ice beam: grass/dragon
return: water/ice
surf: all other types
you will beat everyone of the elite 4's pokemon in one hit