My advice is similar to what others here have offered, but from two directions: first, lots of S8. It instant-kills them, so spam as much as you can. Helios Crisis teams are a good start, but don't forget about a Riptide with ion accelerator (and fusion, for good measure), Hammerhead with ion cannon, cyclic ion blaster, Razorshark with ion turret and Pathfinders with ion rifles. Combine that with pulse/burst cannon spam, augmented by a Cadre Fireblade, Ethereal or both. Basically, force as many saves as you can, and of those, try to make as many as possible cause instant death to maximize the effect of any that do fail.
AP doesn't matter, so just focus on as much volume of fire as you can muster, and make as much as possible S8 or greater. Boost it with markerlights, don't bother stripping cover unless it's 2+.
Remember that he can only assault one unit per turn, and Wraiths have stinky Initiative. Vectored retro-thrusters can give your Crisis or Stealth suits a fighting chance of escaping. Bring drones so you're testing to escape on I4, and gun drones also provide that all-important dakka. (And pinning, in case it ever matters.) You can blind them with photon grenades; I haven't tried this but it could soften the blow a little if they do get into assault.