How to repair this scratch in laminated countertop?
Short of replacement, I don't think there is much you can do to completely hide the scratch.
You might be able to make it less noticeable by coloring it a darker shade so it doesn't stand out as much. The simplest example would be to draw in the scratch with a thin brown marker, although since this is a kitchen you might consider a food safe dye of some sort (they do make non-toxic permanent markers).