Yes, over-optimising your website can actually hurt your rankings rather than help them. Known as keyword stuffing, cramming too many keywords into your content in an unnatural way is penalised by Google. Similarly, building a large volume of low-quality or spammy backlinks rather than earning genuine links from relevant, authoritative sites can trigger manual penalties or algorithmic demotions. Over-optimising anchor text with exact-match keywords, creating thin or duplicate content just to hit a publishing quota, and using manipulative tactics collectively called black hat SEO are all ways to overdo it. Google’s algorithms are sophisticated enough to detect unnatural patterns.
The guiding principle is to optimise for users first and search engines second. If something feels forced or artificial, it probably is and should be avoided.