Original: Red dwarfs such as Proxima Centauri are far too faint to be seen with the naked eye; even from Alpha Centauri A or B, Proxima would only be seen as a fifth magnitude star.
Simplified: Red dwarfs are usually far too faint to be seen with the naked eye. Even from Alpha Centauri A or B, Proxima would only be seen as a 5th magnitude star.