Second hand iPhone
I got given an iPhone second hand that I factory reset and it needs activation lock iCloud log in which the previous owner doesn’t know as they have a new account but the phone won’t let me in without logging in this way
iPhone 8
Question marked as
The previous owner needs to remember their Apple ID and password to unlock it. There is no other way.
See What to do before you sell, give away, or trade in your iPhone or iPad - Apple Support
There are links on that page for help remembering the Apple ID and password.