[jrrrrrrr]

You could try Perish Song, Taunt users (although these are rare in adv), Heracross, or just building your team with no reasonable way of letting it come in. Most sandstorm teams, for example, will give Curselax difficulty coming in. Choice Band Metagross also does a really good job. Sometimes Gengar can be awesome too because Curselax rarely uses Shadow Ball.

It's just a really really good pokemon.