I want to end what I perceive to be a friendship that is just becoming mentally draining on me
What about this friendship in particular is draining for you?
If you are nearly always discussing person's weaknesses, it's no longer a friendship.
Your friend may just be a little bit self-conscious and is looking for a friend to boost their self-confidence.
Shut the fuck up.
I really think you should try to put yourself in their shoes and reconsider ending your friendship with them.