Also, donโt leave your account unused, delete it. User and follower numbers count.
And least as important, reply (if necessary to another corporate mail address) every email with Twitter/X in the footer, with a kind request to stop promoting and facilitating X.
Understandable, especially when there might be a lot of links to the profile around the internet. However, in that particular case itโs still possible to delete all content, contacts / follows, followers, and profile images and descriptions etcetera, make the profile private, and give it some semi-permanent dead existence, or delete if a year later or so.