Google's John Mueller said on Twitter that Google does not issue manual actions, search ranking penalties, over a single bad link. The only way to get a manual action is to have a lot more than just one bad manipulative link.
Of course, to most of you, you know this already. Doing one bad thing, when your site does thousands of good things, isn't going to result in a penalty. One bad link is not going to get someone at Google to penalize your site with a manual action. But if 15% of your links are against Google's guidelines, sure - that could trigger something.
The tweet came up because someone said that the link example Google gave was already nofollowed and thus why do they have a manual action. In which Google's John Mueller said maybe that specific link was nofollowed later but either way, it is not just about one single link.
Here are the tweets:
That sounds like a mistake or something changed on the site. Manual actions aren't based on a single link, so probably the problem is relevant even if the example is a mistake.
— John ☆.o(≧▽≦)o.☆ (@JohnMu) August 14, 2018
How many strikes does one site get with Google?
Forum discussion at Twitter.