To be glad to see the back of

Context #1: Kim and Derek are at work sitting in the break room. They begin talking about their co-worker, Fred.

Kim: You know – Fred was late again today.
Derek: I’m not surprised. I had to finish his last project because he wasn’t here to do it.
Kim: Does the boss know?
Derek: The boss knows now. He is pretty angry. I heard the boss tell Fred the next time he’s late or his work isn’t finished, he’ll be fired.
Kim: That’s fine by me. Fred’s lazy. Actually, I’ll be glad to see the back of him!

Context #2 : Joe is writing a post card about his experience at summer camp…

Dear Mom and Dad,

I can’t believe I’m still here. Every hour seems to take a week! I really miss you and I miss home. It’s cold here. The other kids are really mean. I can’t sleep in this uncomfortable bed. Also, the activities are boring. I’ll be glad to see the back of this place!

Love, Joe.

Meaning: We use this idiom when a person or thing is part of our life and is not liked. A similar idiom is “to be glad to get rid of.” When you “see the back of” a person, it means that person is leaving. In other words, if you are “glad” to “see the back of” someone, you are happy that person is leaving.
https://languagesystems.edu/