I've looked all over the place for hours trying to find this answer with no success. It seems simple, but apparently is not

In general, this is what I'm trying to do:

I want to find values in a second column that are duplicates of values in the first column, and delete those second column duplicates Without deleting the duplicates (which do exist) in the first column. I've tried it all, and have only figured out about 300 ways that Do Not work. Hopefully someone here can figure out one way this Will work!

thanks in advance
-Ryan