This is the end movie of Episode 2 of Duke Nukem 3D - "Lunar Apocalypse". After defeating the Overlord, Duke Nukem proves himself as a man of honor that keeps his word. The first sentence he's saying to the Overlord when he sees him is: "I'll rip your head off and shit down your neck". This video also includes the battle itself.
[This is the PC version] [Thanks to DOSBox team for creating the 8th wonder]