How many hits does it take you to kill an Enderman with a diamond pickax?

It takes a total of 7 hits with a diamond pickaxe to kill an Enderman in minecraft. This is because the Enderman has 40 health points (20 hearts), and a diamond pickaxe deals 5 damage (2.5 hearts) per hit. However, it's important to note that using a pickaxe is not the most effective method for combat, as sWords or axes are generally more suitable for dealing damage to mobs.