One of the best is the Paraphrase Tool, which handles more than 100 languages and 15 free paraphrasing modes. It's based on the latest AI technology and comes with features like a compose mode to turn keywords into paragraphs, a plagiarism detector and several writing styles. It's good for writers who have to do lots of different writing tasks and need to get them done fast and well.
Another good option is Rephrasely, which can paraphrase in more than 100 languages with 12 free and 6 premium modes. It also can generate paragraphs and check for plagiarism, so it's a good all-purpose tool to help you write faster and avoid plagiarism.
If you want something more flexible, try LanguageTool, which works in more than 30 languages and dialects. It's got grammar checking, tone suggestions and paraphrasing, along with the ability to integrate with many writing tools and websites. That makes it a good choice for professionals and academics who have to write in multiple languages.