There is no one-size-fits-all answer to this question, as the answer will vary depending on the specific facts and circumstances of your case. However, generally speaking, you cannot be sued for defamation or invasion of privacy if what you write about someone online is true and factual.
You may also be immune from liability if what you write is opinionated or expressive rather than factual. However, if what you write constitutes defamation or invasion of privacy, you may be subject to legal action regardless of whether it is considered opinion or fact.
Ultimately, it is important to remember that anything you write online can be used as evidence in a legal proceeding. So be sure to carefully consider the consequences of your actions before posting anything online.