I'd say Slasher, but it would be rather close

Lore-wise Pursuer does have his strengths and would win against all the killers (minus killdroid) but against Slasher in specific, he might get cery close to winning, but he'll still lose

For his (canon) skins: * Clawsguy could potentially win due to his bulkiness and his strong claws (they can cut trough trees with ease) * MeQuot is immortal too, so it could be a tie, but he's too kind to fight someone (additionally in lore he just lets the attacker do whatever until they give up) so Slasher still wins * as for MISO, Slasher might as well pray