Hey there, it is not possible to unlink an account without authenticating it. Bungie does not forcibly unlink accounts or cancel cross-save. Also note that PSN is your Active account in your cross-save setup, meaning it is where your characters and your progress are located. Currently you can still access those characters by playing on Steam, but to want to abandon this PSN account specifically (if you could regain access to it) would mean you are losing the current characters and all progress on that account. With that in mind, you could simply continue to play on Steam with this otherwise-inaccessible PSN account linked, and things should still work fine. Now I've mentioned that trying to get rid of the account would mean abandoning the characters and progress, is there any other reason you want to get rid of the account or could you just continue to play on it through the linked Steam?