The ender men are the hardest mob to kill. Not the ender dragon, because that is a boss. Since they can teleport, it makes it really really hard to kill them.

Ups: they give you ender eyes. which can be made into eyes of ender which are used to go to the end. Ender eyes teleport you to wherever you throw them.

Downs: Ender men can teleport, making them extremely hard to kill with a sword. They also take bricks out of things like you house or the ground. I don't think they can take chests.

Ender mens attacks are very strong, and it takes, and it takes a lot of hits with a sword. They hate water, so if you are to go hunting for ender men, go hunting in the rain or bring a water bucket. They also don't die in the sunlight. Endermen also can't get hit with bows.