Google’s John Mueller said that most websites do not have ‘toxic’ links. If they do, they usually created them on their own:
Most sites don't have "toxic" links, or at least, created them on their own. IMO there are more important things to focus on, by our engineers, and definitely by site owners.
— ? John ? (@JohnMu) January 28, 2020
Toxic links are spam links that have a negative impact on your search engine rankings. If you built spam links in the past, use the link disinfection tool in SEOprofiler to get rid of them: