It's a brick unless you can trace the last owner and get them to close their account which iis linked to that phone. You cold try a Factory Reset but I've known units where that fails as well.
Switch off then hold down the Volume down button and switch the phone back on.
If you get that far, you need to tap the Volume Down button seven times to get ti the Factory Reset option then accept that. The process might go through and wipe any data belonging to other folks but I have known it to fail completely. The first time it powers up after the reset, it still wants that old login.