The Invincible Iceman

Perfect defense without the defence. Never defend against an attack and never take damage you don't choose to take.

The key combo here is Iceman and Northstar. If you get enough readies (Utopia, Professor X, Cryokinetic Perception, Ever Vigilant and What Doesn't Kill Me.) Iceman is capable of bring the opponent's attack to zero. But Frostbite does not prevent boost damage/scheme. That's where Northstar comes in. With enough healing (#Med Team, #Triage) and #Protective Training Northstar can cancel every single boost card.

Then, because you aren't taking much damage, and Power Belt gives HP, lean into that with Dauntless and Fighting Fit to increase damage output. I included Endurance to give a buffer to make sure this engine doesn't break.

But there is a loophole, What Doesn't Kill Me is great, but you need some damage on you for it to work. That is where Rogue comes in, she gives a controlled drip of damage on Iceman that you can heal while being able to hit for four damage. She could potentially use the healing too to stay in play. A second Protective Training could work too.

Iceman should never use basic thwart as it doesn't Frostbite. So allies need to handle thwarting.

I do wonder if Deft Focus, Power Belt and X-Gene is overkill. Power Belt can pay for Snow Cloneas well, but they are a low priority ally. Deft Focus is slightly better than X-Gene because it works on Cryokinetic Perception. So X-Gene could be dropped for a second Protective Training or something like Energy Shield to control any excess damage.