The first thing is to identify the reason behind the SEO penalty
Go to google search console and see for notification or check security & manual actions tab in google search console.
Your First Option - Reconsideration Request
Before you go for Reconsideration Request, make sure you have identified the reason behind the seo penalty, and you have also corrected any violations of the guidelines, once this part is done you can request reconsideration to have the manual action revoked, so that google can reevaluate your website and again you can work in your website SEO
When not to file Reconsideration Request
If you can't find any manual action or notification on your site but still see a drop in search results and rankings, it's possible that your website was hit with an algorithm update. In this case, you should not file a reconsideration request because it's only applicable to sites that have violated Google guidelines, such as buying links.
3 major reasons why websites get penalized by Google for violating their guidelines?
• Spammy blog comments
• Auto-generated forum posts
• Buying back-links or spammy backlink profile
If you want to avoid the Google guideline penalty, make sure your website is free of spammy comments that add no value to the content or comments generated by bots; keep deleting these types of comments to maintain the quality of your blog content.
The same is true for forum posts; make sure that when you post something on a forum to create a backlink for your website, the content is of high quality and relevant to the discussion; otherwise, it may cause problems for your website.
Buying backlinks - Many website owners invest heavily in link buying in order to boost their rankings quickly, but keep in mind that if Google ever catches you, it will be a terrible day for your website and it may never recover, so it's best to avoid any link buying practises.
So How to Get Rid of Bad Backlink Profile
In many cases, the website owner does not engage in any backlink practise, but their website still receives a large autogenerated link profile, which may harm Google rankings and, in the worst-case scenario, may result in your website being penalised.
• First you need to relax
• Identify poor quality links pointing to your site
• Try to get them removed or marked as "nofollow"
• Use the Disavow Links Tool for any remaining harmful links
• Be careful when using the tool and only disavow truly harmful links
• Watch Google's video to avoid common mistakes when using the Disavow Tool
Since, you have done some real work and did your best to regain google trust, do not forget to document the journey, you may take some snap’s to share it while submitting your website for reconsideration request, it may benefit you greatly.
Now you might be wondering how long the process will take to resolve?
Well, there is no guarantee time frame but you can expect it to be reviewed by google employee in few days and you will get notified, and you will be again notified once the manual action has been revoked
In you want to know more about it you can visit google webmaster forum community