Updated on
At the moment Spotify does not offer an easy way to remove a podcast completely.
The easiest way is to delete your Spotify account entirely, which removes all the podcasts linked to it as well.
See:
https://support.spotify.com/us/podcasters/article/deleting-your-account-or-podcast/
Do you not want to remove all your podcasts?
You can always create a new account at Spotify and submit the podcasts that should stay available on Spotify again.