He-Man and Lion-O vs Aku and corrupted Ashi

Who wins?

Assuming their weapons could actually harm them, He-Man would effortlessly solo. He has a level of physical superiority far above any character in Samurai Jack IIRC.

He-Man being there renders Lion-O more or less useless. He-Mans plot device magic sword would probably work just fine, and he has insane levels of strength and speed.

As KMC's only Thundercats historian, Lion-O could potentially solo as well. While he hasn't shown the plot-strength He-Man has, he has:

-easily cut through massive boulders
-bested Panthro who likely a 100+ tonner in the Trial of Strength (one of the test to become Lord of the Thundercats)
-lifted and flipped over the ThunderTank as easily as pressing X in Halo to flip the M808B Scorpion
-dodged and deflected multiple incoming lasers with ease.

👆

Don't forget about pulling Safari Joe's ship back down to Third Earth as it was attempting to escape the atmosphere. (Still nowhere near as impressive as He-Man holding back Horde Prime's starship with warp engines running, but it's nothing to sneeze at.)

I would be willing to bet the Sword of Omens would work better against Aku then the Power Sword would.