An article published by SEMRush discusses on how SEO experts fix and avoid penalties from Google.
Here is Jason Barnard’s contribution to this article:
As Jason Barnard (The Brand SERP Guy) suggests, go for a “full humble” approach, when contacting Google — this is not the time to say you were right, argue your way forward or blame a third party. Moreover, it is better to apologize and say you won’t do it again.
Simply put, take responsibility for your mistake, even if you had no intention to mess with Google’s search engine. Show that you are “truly sorry and redeemed”, as Angelo Vargiu says.
Fili sees the whole process as a multitude of steps that need to be taken, including improving both content and technical on- as well as off-page signals. That having said, every penalty can be lifted and almost every website can gain more relevant visibility after a penalty is lifted and the website has been improved with SEO.