Activation Lock is designed to prevent anyone else from using an Apple Watch if it's ever lost or stolen.
About Activation Lock on your Apple Watch - Apple Support
Activation Lock is an anti-theft feature that cannot be bypassed. Only the previous owner can remove the lock by using their Apple ID & password. If the previous owner cannot or will not remove the lock, then the watch is useless to you or anyone else.
If you are the ORIGINAL owner, then see the 'Start a support request' section in:
How to remove Activation Lock - Apple Support