Count Dooku is a Sith Lord through and through, but not in the traditional sense. In bituin Wars, and madami specifically Attack Of The Clones and Revenge Of The Sith, Dooku AKA Darth Tyranus tries to reason with the Jedi and Obi Wan Kenobi
Mace Windu's death is one of the most tragic & significant in bituin Wars, and with 4 words, that moment was redefined forever (& in madami ways than 1).