Under normal cicurmstances I think Yuga would have the edge but the recent Rox was above the multiversal divines like Spectre and Radiant. Of course not every monitor is the same but Rox is one of the more powerful ones.
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Iboga chose not to fight, to allow himself to evolve. He had the wisdom to abandon the actions of war when he knew they would no longer serve him.
Normally, guys like Yuga Khan would lose against a multiversal guardian destroyer like Rox Ogama but seeing as he's got those long horns Khan wins by stabbing Rox Ogama to death.
Rox was once an 'average' Monitor, but after his exile he was somehow empowered by Mandrakk. That's why he was powerful enough to tool Spectre/Radiant collectively.