Alright, well there are two different Pokemon I would suggest. If you're looking for a more offensive revenge killer, then Starmie would be excellent for that. You could use the Choice Specs set to basically kill anything you need to. You could also use a Choice Scarf set to be sure that you're going to outspeed the opposing Pokemon, though the power of your moves will be reduced. If you're looking for a more defensive Pokemon then I would go with Unaware Quagsire. It can come in on any Pokemon that has boosted its stats and just cripple it with Toxic or Yawn, and then kill it using Scald and Earthquake. Scald is especially useful because it has the burn chance, and that will allow you to take care of physical threats. Both of those Pokemon can take Water-type attacks well, so yeah. I would replace Mamoswine with whatever Pokemon you choose, because you need the entry hazard support.