The Ending Blow, Spin Attack, and Vertical Spin Attack are all done by simultaneous WiiMote and Nunchuk movements in a specific direction:
Up - Vertical Spin Attack
Left or Right - Spin Attack
Down - Ending Blow
Actualy, the ending blow is context sensitive, when you thrust both remotes down when your not targeting a downed enemy, you'll do a vertical spin attack, only downwards.