New apple laptop is using the previous owners keychain password.

What can I do to get rid of the password block

You need a password or a support request to unlock the Mac. See the support document How to remove Activation Lock for the details. If you have neither a password nor the original sales receipt then the device is useless to you.

The old owner had to do this before selling it: What to do before you sell, give away, or trade in your Mac - Apple Support

If they did not do this, return the computer.

is this activation lock or just login password?

what model-year MacBook Pro?