You get this achievement for defeating a 'Glovey' enemy as Bolt - with a finishing move.
'Gloveys' are the enemies which can been found early on in the game - with the gloves that generate electricity.
A finishing move can be used when 'B' appears above the enemy's head - Hit 'B' and then hit 'Y'.
The 'B' will appear above the enemy's head after a certain number of Bolt's normal X/Y attacks.