There are several types of manual penalties that Google reviewers can apply to a website for violations of the guidelines. Cloaking or sneaky redirects penalty, Unnatural links from your website, Hacked website, Pure spam, and Hidden text or keyword stuffing are just a few. One of the biggest sources of penalties is for unnatural links, both incoming and outgoing. Here are some of the unnatural links that can cause issues:
Web directories / Article directories
Abusing web directories and article directories for incoming links is at the top of the list. The only link directories that escape a penalty are manually curated lists. Even then, Google does not penalize sites but chooses to ignore link lists.
Links from International sites are also a problem when they are a majority of the incoming links. Content on foreign language websites that are not relevant contextually raise red flags. Nowadays, the practice is pointless as Google reduced the weighting on links from other languages.
There are hundreds of Coupon codes sites online, and links from them are considered spammy since most of the sites only exist to provide links. There is often no value to the coupons, and there is no content actually to read.
Another issue with affiliate links that are without the no-follow attribute. Google equates that sort of activity with buying links, and the penalty can be severe.
If you have a site that relies heavily on traffic from Google, then make it a regular practice to use online tools to scan and analyze your backlink profile. When you find problematic links, disavow them immediately. Some sites do link checks daily.