My advice -- review immediately, approve immediately.
Give PR's the highest prio.
Leave your suggestions, but approve the PR immediately and automatically. Then leave it to the other person, don't check it, don't chase. Just forget about it.
For further actions, you may consider blocking this person and/or reporting abuse
We're a place where coders share, stay up-to-date and grow their careers.
My advice -- review immediately, approve immediately.