Steelix is a pretty tough pokemon, but when you’re up against Ash you have to be more than just tough! Ash has a lot of pokemon at his disposal and with them he can pwn as many opponents as he wants!….or a lot of them anyway. Steelix is strong, but Charizard and Pikachu could weaken him. Ash wins.
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Pikachu would actually be usless against Steelix. He’s a Ground type as well as Steel so he’s immune to electricity, and Pikachu’s physical move. wouldn’t harm his tough outer shell, even Iron Tail.
But Charizard could beat him since he’s a Fire type. And if not, Steelix is still weak to water, so there’s always Squirtle, Cynadquil, Totodile, Lapras, Kingler and whatever Fire, Water or Fighting Pokémon Ash gets in other regions
Yeah, Ash has so many pokemon it’s scary! Pikachu’s thunder may not really hurt Steelix, but his Volt Tackle ought to still do some damage. Of course Charizard can do most of the work in this one