No guarantee, but if it were mine, I'd try 0000 steel wool in a back and forth, not circular, motion. This has worked to shine up aluminum gadgets put into the dishwasher by mistake and some cruddy copper objects.

It doesn't look "broken" to me....what's the problem? The knife is stainless?

Can you fix the knife, No. but you can pay a plating shop to fix it.

Contact your local metal plating shops.