If you have observed SEO industry closely for the past 10 years, there have been numerous changes that have kept the webmasters on their toes so as to keep abreast with the changes that Google incorporate in its algorithm. However, nothing has worried these site owners more than the updates that were made in the past 2-3 years. With these updates, the SEO industry has turned upside down. The whole practice of off-page SEO is almost gone. Google has started giving more importance to on-page practices and the overall quality of the website.

For example, consider the link building exercises that SEO executives engaged in. On daily basis, they submitted their sites to directories. They submitted articles in article directories to generate back links from keywords on which they wanted to optimize their website.
With the recent recommendations of Google, off-page link building is discounted and Google asks for quality link building that does not look low-quality or unnatural and should be very relevant to your website. Unlike past practices, contemporaries say that SEO professionals should be focused more on quality of the content and the website in general rather than mindlessly generating unrelated backlinks.

In the present scenario where Google is almost manually looking at everything that you link from your website and also everything that links your website, it is better to have a close watch on your backlink profile and to remove the negative or unnatural backlinks. To avoid penalty from Google, webmasters need to do it proactively.

At the same point, it is also important to notice the anchor text of these backlinks and no unnatural weightage should be given to them.

If you find that Google is penalizing you for unnatural links, the best way is to start a systemic link pruning campaign. After you have diligently removed questionable or low-quality links for your website, you can resubmit your website for reconsideration.
Google is looking for sincere efforts from your side to remove those links. It wants you to make at least three outreach attempts to remove those links. If still you are not able to get that link removed, you may document it in your pruning list and move on to other links.
If you want to quantitatively figure out, the sites that are penalized for unnatural links will need to at least remove 85% or more of the identified low-quality or unnatural links to make sure that they recover fully from the penalty levied by Google on them.

It becomes highly imperative that webmasters keep a close eye on backlink profile of their website so as to avoid penalty from Google. If Google has already penalized your site, it is more important to diligently work on the profile and try to weed out every identified link that looks low quality or unnatural.