Assuming you mean Hal/Parallax rather than the yellow bug?
Well, Yellow Bug, I'd just go with Mxy.
The other way...tough to say, both have universe anihilating power. Both have only really been shown to be below Spectre, and that's about it. When Spectre destroyed magic, Mxy was powerless, in Zero Hour, Spectre was insturmental in stopping Parallax.