You get this achievement by killing a 'Disky' enemy as Bolt with a finishing move.
'Disky' are the bigger enemies which throw the frisbees (sticky mines.) They appear quite often during Act 3.
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 Bolt has dealt enough damage, it is difficult to hit these enemies with normal attacks so it would be easiest to use Bolt's Power moves to get their health down.
There is a 'boss' Disky, at the start of the 3rd Act, at the end of the section with the train. (Chew Chew Train).