The act of dunking on someone so hard in a competitive aspect, whether in sports or anywhere else to the point where they may question their religion and consider attempting suicide.
The enemy team was megadunked so hard they disbanded and renamed themselves one day later.
Smot was megadunked so much that he lived the rest of his days out as a fisherman.
The act of engaging in violent sex with a woman, accompanied by megadethmusic, in an effort to get her to relax, and loosen up her usually solemn demeanor. Used in reference to very attractive, though cold and detached women.
Hey did you meet Shannon from HR? She could really use the megadeth treatment.