Hi I got a locked apple watch sold by a scammer

There is unfortunately nothing you can do about it unless you can convince the scammer to refund you what you paid. Apple will not unlock the Watch for you unless you have proof of ownership such as the original purchase receipt from Apple.

that's the world we live in. Take this as an L.E. to never buy any Apple products via a third party source or via anyone who isn't an authorized seller of apple products. That really goes for most high end smartwatches orphans. Best thing to do if you decide to go that route is to personally get in contact with Apple customer service and provide them with the serial number of the item your interested in purchasing and they will provide you with its history and let you know if its not reported stolen/blacklisted/paid off/not in contract/ or STILL ACTIVE ON SOMEONES ACCOUNT......

This may not help in your case, but I recently sold my old Series 3 when I got a new Series 8. I went through the process provided by Apple to unpair and erase the Series 3 (and double-checked the same info on YouTube videos). When signed into iCloud the Series 3 watch was no longer listed after that. Fast forward to the buyer telling me the watch was locked. I contacted Apple via chat only to learn that I had to additionally go into the 'FindMy' app and delete it there. No explanation of why it would be removed from my iCloud list of devices but still be on FindMy. That resolved the buyer's issue. I have not seen any mention of having to separately remove an item from FindMy in any instructions for selling a used Apple Watch. Maybe it's out there, but I have not seen it when revisiting the directions. I was accused of selling a locked device due to not knowing the separate FindMy issue. Thankfully I was able to resolve it for the buyer.

Bummer.