Kingdom Hearts II/Heartless

Shadow
The most common heartless. It is pretty easy to beat.

Soldier
Can attack with a few different moves. Parry it's attacks and use Cyclone to finish off it and surrounding enemies.

Nightwalker
It is resistant to beginning magic. It is easily defeated even with the Kingdom Key.

Rapid Thruster
One of the most common enemy in the game. In large groups, use Aero Trap to defeat multiple Heartless at once. In small groups, just jump and attack.

Bulky Vendor
The rarest Heartless. It is found anywhere breakable objects (suits of armor, fireworks stands, etc). Wait as long as possible to use the Reaction Command.