Dont see how spike is a nihilist. Like hes pretty laid back most of the time but not really anything else. A good nihilistic themed anime would be Texhnolyze, one of the main characters has alot of nihilistic thoughts. set in a world where humans are drove underground (Its revealed why near the end and its a very trivial reason), its very slow paced but gets very intense at the end. Theres alot of big dark empty rooms setting the scene, poverty, sadness and the like. The main main character basically gets a robotic arm and leg (Hence the term "Texhnolyzed") after getting attacked. He doesnt want them but gets forced to. He is reckless, doesnt see a purpose in living and doesnt care about morals and anything else.He brutally murders someone in this anger. slowly he calms down after meeting one of the other main characters and just follows his orders no questions, also rarely talks to show how empty he feels. Near the end, he sort of accepts the emptiness and brightens up. Although for the other 2 main characters, it doesnt go so well. It left me feeling extremely empty but with a different outlook on things. i gave the series a 9/10, although this series is not for everyone as it is very serious, dark and slow paced.