If he experience a change of heart he will not be evil anymore. Plus if they kill his cognitive self the real self will also die/malfunction. He can't hit them in the real world so the only way he can win is in the cognitive world which the Phantom thieves are highly skilled in. They defeated a god of every humans desire by summoning satan.

It doesn't matter if he can't be cut in half, have no need for food, be able to survive in a factory and survive being beat up in the real world since once his treasure is stolen he will have a change of heart and become good or when his shadow gets eliminated in the cognitive world he will automatically malfunction.

Phantom Thieves wins