I always find it interesting to read how black hat SEOs deal with penalties. A Black Hat Forum thread has one that said their rankings dived after participating in acquiring links within a PBN (private blog network).
The advice quickly given by others were "don't panic just yet though, whatever has happened you can fix it!" Encouraging!
The first thing this person said was to wait a few weeks and see if anything changes and improves. If not, then it is time to drop the links and disavow them. Of course, check to see if there is a penalty in the Google Search Console (if the site is verified) and go this approach.
Of course, if no recovery, the churn and burn method is something they are use to. Just kill this site and start a new one, rinse and repeat.
Black hat SEO isn't what it use to be but it is still interesting to see how some adapt.
Forum discussion at Black Hat Forum.
The image is from the Google Douglas Adams Doodle.