Fernus VS Thanos
Fernus vastly increases the strength of the powers he inherits from J'onn: for example, he can phase other beings rather than just himself, and he can telepathically control the other Justice League members, rendering them unable to fight him. He can breathe fire of such intensity it harms Scorch, who had previously been thought immune to damage from fire. Fernus' tremendous strength also allows him to dominate the Justice League in combat even without his Martian telepathic powers. He can also heal himself from almost total destruction within seconds.
VS
Thanos, before he was killed.