This “professional hacker” will simply compromise the next Apple ID, and the next, and the next.
You’ll want to figure out how the compromises are happening, and either prevent that from happening again, or take steps to mitigate the compromise. Which may well be feasible within the existing Apple ID.
Otherwise, whatever happened previously likely repeats.
This all assumes a compromise, and not some other issue or explanation, too.
As for Activation Lock, you’ll need to release that lock on all devices before deleting the account. (If you don’t, you’ll then need to request Apple release that lock, while providing proof of ownership sufficient to convince Apple. Or recycle everything still locked.)