Ash has made countless Pokémon friends on his adventures, but some are often regarded as his most powerful allies.

Ash faced numerous Gym Leaders throughout his journey, so which one stood out as the toughest challenge in each region?

As it is his home region, Ash's original adventures took place in Kanto, right after he left his home of Pallet Town in the first episode of the main Pokémon anime. There, he captured several Pokémon, ...