Infernape outspeeds it and resists it's priority Sucker Punch. He has access to STAB fire attacks which hits Mawile's steel typing very hard.
Blaziken can also handle it very well for the same reasons as Infernape.
Ferrothorn resists it's moves if it's running duo STABs with Sucker Punch and SDance.
Mega Medicham can KO with Fire Punch.
Rotom-W can outspeed it and is not affected by Sucker Punch when using status moves like Will-O-Wisp.
Excadrill can survive unboosted priority and KO with STAB Earthquake.
Thanks to Jojo for his assistance.