If you just want to annoy them bury them in skinks. Other than that to kill them you can bring what's already mentioned. however two potential units have been left out.
- Shadowstrike with Chameleons, you're going to bring the shadowstrike anyway, bring some chameleon skinks. 32 of em in a shadowstrike host will kill a great unclean outright. They'l provide some much needed firesupport for your rippers to Ensure the kill.
- A sunclaw host, but not necesarily at maximum strength, alongside some big scary stuff for distractions. Even without the horde bonusses (and without alpha's) you only need 40 saurus in a sunclaw host to kill the great unclean one. Basicly, a minimum sized sunclaw starhost of 3 units of 10 alongside their sunblood stand a decent chance of killing an unclean one in a single turn. Now bring 3 units of 20 and they'l shred the unclean one to bits. And since everyone is used to saurus warriors being well, garbage, outside of massive, buffed up, hordes, chances are your opponent will likely not even bother harrasing a 20 man unit of saurus and instead focus on taking down your big shiny dinosaur whom you keep on saying is amazing and is going to nom his great unclean one. Admittadly, he's only going to be caught by surprise by this once.. Though even if he knows it's coming it's a very cheap way of distracting him from other potential threats. A 10 man squad of saurus warriors in a sunclaw host puts out a potential of 41! wounds against a great unclean one on their own. That's a rather powerfull threat, scary enough to get him to make mistakes.