Due to the negligence of the previous owners my frame is badly scratched. Is there a way to correct it without paint?

Where abouts is it scratched?

I doubt it's worth it or possible to fix unless it's only a very light scratch.

For what it's worth my race NC has deep scratches on the swingarm from poorly fitted rearsets (a lot of NCs seem to), but I just live with it

Sticker it, or get some carbon on there?

Polish them out then use a scotchbright pad soaked in ally cleaner to dull the polished finish to get it looking close to standard. Plenty of elbow grease needed and wont work so well on deep scratches.

This frame was covered in scratches, looks pretty decent now but to keep the finish nice could do with a coat of laquer.

Painting a frame is twaddle!

The scotchbright & ally cleaner works a treat after polishing or just bang some carbon covers on there as Alex says but me, i'd just have it blasted & powdercoated.

Its a fair bit of work but looks good & well worth the effort - if you add up all the time it takes to polish it, clean it up etc & buy whats needed, you're half way there to getting it powdercoated.
& the carbon coveres cost just as much as my powdercoater charges to do a frame & swing arm!