Can only Tik Tok send a lawyer's letter to the other party?

No. If you encounter infringement on the Internet, for example, someone secretly sent it to Tik Tok, a blogger of Tik Tok moved the video, or copied it, and so on. Anyone who causes infringement can send a lawyer's letter to the other party. A lawyer's letter refers to a professional legal document made and issued by a lawyer to disclose and evaluate relevant facts or legal issues, and then make a request to achieve a certain effect.