Poison and killing blow. Poison the guy to death with a couple of units of skinks. Oxyotl is a special character that can snipe characters out of units. I don't normally recommend him but he's an option. Also killing blow does not allow armour saves. So throw a cheap character at the beast and get killing blow off once = Game over for Chaos on Juggernaught. You can also avoid that particular bit of nastiness. The thing with Chaos is that players whom dump a crap ton of points into a character or characters has a smaller and smaller army. Focus on the rest of his force and avoid the real nasty guy(s)/gal(s) and you've got it made.