Cleaning up digital accounts

We all have accounts on dozens (hundreds?!) of platforms. In its peak, my password manager had almost 200 entries, 80% useless. All this idle data is still sitting in databases and servers somewhere, using natural resources to be stored, analyzed, migrated etc.

Here I want to document the process of deleting my accounts and their data from services I don't use anymore.

@edit: I stopped documenting the deletion process, since it may change.

Not able to delete