It has been a week since my steam account recovery, due to an email hack. After having all my passwords changed and activated all kinds of two-step verification, I have noticed that everytime I login Destiny 2 my characters are not the way I left them previously, and also on the "Collection" tab ingame some loot has been acquired on characters I don't play anymore. Is there a way to kick this "invader" out of my destiny2 account? All kinds of security measures have been taken, concerning my email, steam acc, epic acc etc...
If all the linked accounts are your own and they're still able to access D2 then it means you haven't secured your platform accounts.
Contact your platforms support for your platform accounts and see if they can invalid all sessions to force a new sign in.