I been using amber on android but have my nsec saved in a txt file in cold storage just In case (im case being telling everyone my new account because the old was compromised) i did see freeform gives a option to delete "account" my best guess is this is your best chance at clearing a nsec.

I noticed you can delete post yourself If the relay supports that nip. I also noticed that amethyst supports delete requests but seems to be only posts made from amethyst (i dont know why just a observation)

People think you cant delete stuff on nostr ***wrong*** if every relay you brocasted to decides to delete all data, then your posts are deleted. Thats why there is options to back your npub up in many ways. So then later you can re brodcast, Or run your own relay. I'm sorry if i got off point. Just hope this helps people understand relays and nostr