Endeavor is a Normal move that neutralises the combatant's Hit Points. It is often used in the F.E.A.R. battle technique.
A very useful move, as your opponents HP is turned to yours. This TM can be used to win any battle, if used correctly. For example, if you have an Tepig that has learned the move endeavor by it being hatched from an egg, you simply have to give it the quick attack TM, and an item that will replenish its HP every turn. This is known as the F.E.A.R. tactic. For more information on this tactic, click the F.E.A.R. link above.