For messenger, at least if you're registered just in messenger with a phone number, you can "delete" it by re-installing the app and attempting to re-register w

For messenger, at least if you're registered just in messenger with a phone number, you can "delete" it by re-installing the app and attempting to re-register with the same number. When it prompts you to use your existing account, say it's not you and then choose a new name. This seems to reset your contacts and history. No idea what it looks like on the back end, assuming facebook is still rolling history associated with the number. There used to also be a pathway to promote your messenger account to a full facebook account and then delete it that way, but it's been a while so not sure if that's still possible. Not sure if you can pull of similar against email based accounts though.