Unfortunately, there is no quick way to find out who unfollowed you. I am forced to make a list of follower names every time I get an email from Medium that informs me of new followers. I have that list alphabetized in a document format. Here is where it gets to be a pain in the butt. Medium does not alphabetize your follower list or following list in your profile page (one of my major complaints, it’s not like it's hard to do on their end). You can spend an inordinate amount of time searching through your follower list against the list you made from your email notification and see who is missing from your profile follower list. That would show you who unfollowed you. I wish Medium would make the follower list searchable by name. I find this to be tedious. What I do now is every 2 weeks, I will take the email notification of new followers and go to each name's profile page. I click on the name’s following list and search for my name in the drop-down box. It’s quicker than my old way, especially as you accumulate hundreds and hundreds of followers. Who has the time to go through each? Medium could easily notify us of who unfollowed us, but they don’t. Hope that helps you.