I think it's only fair that I take another student's test paper after they destroyed mine.
Why did they destroy yours?
They were frustrating me all the time so I scared them. In retaliation, they destroyed my paper.
You both need to stop getting revenge on each other. Just because they destroyed your paper, doesn't give you the right to take theirs. If you retaliate, it will just make them angrier and want to do something mean to you again.
It's not like it's going to deprive them of an education and it was funny. If I get my admin involved, she can just make a new test for me.
I think getting her to make you another test paper is a great idea. That might be a good start to ending this revenge cycle, so the two of you can feel more relaxed.