How could you mention such evil!!! J/k. I'd say the best bet is to blast him from range or take out every other Necron so it phases out. In CC it's nearly impossible to kill him. You can do it with a Warboss and very large bodyguard with Powerclaws in CC but that's if he doesn't kill everyone. You can also do so with a large mob of Ork Warbikes. Although you need 6's to harm him you can still get a small amount of wounds since the Big Shootas are Assault 3 Twin Linked. Take a Kannon, a Kustom Mega Blasta, Mad Dok with Urty Syringe, Uge Choppa, a Lootas Devastor Squad, a looted vehicle, or a Zzap Gun. I'm telling you though, make the sucker phase out!