Hello,
I understand how spammy backlinks can ruin the performance of an SEO expert for a website. I've also been faced the same issue where my competitor made some spammy backlinks for my website and I triggered it out.
I simply made a text file mentioning those links and domains and upload it in google disavow tools.
You can check it here:
https://search.google.com/search-console/disavow-links
I hope this will help for you.
Thank you.
