Deactivate sounds like Facebook. It's actually deleting in this case.

It calls "You can deactivate your account now" on the above note. So Deactivate makes sense instead of Delete. Also Android & MacOS is using "Decline & Deactivate" string

Revisiting this: Android and macOS have Deactivate, iOS and TDesktop have Delete. They have different meanings (making an account dormant versus nuking it from orbit) -- are the different platforms actually doing different things here, or should they all be unified into deletion or deactivation?