What to do against Bad-Seo against my niche site?

I recently discovered a very bad Link from a bad PBN-Blog linking multiple times to my page and linking my pictures. Stuffed with keywords and so on, perhaps you know these kind of sites.
The Blog also links to some other (big) concurrents in that very niche.

I submitted the url to google, asking for deleting it and I hope my serps are gonna get better again now in a few days.
But I'd love to find out, which one of my concurrents is using these bad domains to kill other ones serps.
Of…

What to do against Bad-Seo against my niche site?