To easily defeat armoured foes use the triangle + roll trick to go behind the enemy and attack. While he's on the ground use the triple somersault attack (Crouch + Jump then attack) and a part of his armor will fall off. Repeat until all his armor is gone, then defeat him normally. Against turtles, the roll trick won't work. wait till he's about to attack and while his defences are down, attack. Use the triple somersault attack and his shell will fall off. Then he will look more like a frog. Again, defeat him normally.
Submitted by Abhijit Jassem