Originally posted by Cogito
There are very, very few characters/objects in comics that Mxy would lose to if he didn't want to.
This.
Remember, even though non-canon to a degree, it took the combined power of the Quintessence to even injure an alt reality version of Mxyzptlk when caught off guard. That's the combined might of Shazam, Zeus, Ganthet, Highfather and the Phantom Stranger.
Was that even canon? I don't remember the events of that crossover being mentioned in the Cube's OHOTMU entry... Or in any other source(s). You know off-hand if it was?
If not, I guess it makes sense. Valiant and Marvel are completely different companies, afterall- and usually cross-company comics (Marvel vs. DC, for instance) are regarded as non-canon unless we have reason to believe they are canon.