The Death of Alien Metron Jr.

At the climax of the first act of Ace's rematch against Alien Metron Jr. and Doragory, Ace manages to deal with the alien in a particularly badass yet simultaneously gruesome way, courtesy of his Vertical Guillotine, cutting him neatly in half lengthways! Still, the battle isn't over; as Ace's Colour Timer begins to blink, he now has to face off against the extremely-strong Terrible-Monster Doragory, who's still able to put up quite the fight.

Example of:
Half the Man He Used to Be