Most Challenging Monotype Pokemon Playthough

[Xxain]

Depends on type and what gen your playing. For example a Fire type run in gen run in gen 1 could possibly be tough. You start with Charmander and your next types are not till celadon, Flareon and growlith/Vulpix, then Magmar/Ponyta

The beginning of gen 1 is not geared towards Fire types: Mt Moon, Rock Tunnel, Starmie with a mean bubble Beam, Brock. All with one pokemon, unless you trade but that removes the challenge.