You can add "you know?" to the end of a sentence. One occasion to do this is when you're criticizing someone. Specifically, this is the situation:

Someone has a bad quality, like being "a pain in the neck".

• You've always known about this bad quality, but tried no to say anything about it.
• They do something that makes you even more annoyed or mad than usual.
• You feel like you have to complain, so you say "___, you know?"

For example:

You're a real jerk, you know?

You're really not a very good listener, you know?