Both these guys have kicked the living crap out Thor, and just about everyone else they've come up against.
Mangog is a contender for the strongest being in the universe (excluding the cosmic-gods like Galactus or Eternity), rivaling Thanos, Drax (w/Power Gem), Gladiator and Champion.
IMO, he could be one of the few beings capable of defeating the Hulk in hand to hand combat. In fact, I"ve never seen anyone dominate Thor in hand to hand combat like Mangog has. He pummeled the living shit out of Thor, and even took a God-Blast with no effect. He even chewed on his head. Brutal.
Kurse is also someone not to be taken lightly. Powered by magic, he is practically unstoppable. He once had to be dropped into a volcano in order to slow him down (In fact, if I remember correctly, that was just to stop his previous elf form, before he became the even stronger Kurse.)
He has beaten Thor to a pulp, and pretty much wades through entire battalions of Asgardian warriors and trolls like he was walking through long grass.
Whenever he fights Thor, Thor usually has to resort to some kind of magical weapon or trick him into defeat. I haven't seen Thor ever beat him under his own power (not to say that he hasn't, just saying that I haven't seen it, so if there is an example feel free to scan it and show me.)
Anyhow, onto the fight. Not much of a set-up. These two fight on Battleworld, so as not to destroy anyother planet they fight on.