>>154549Perfect Blue and Paranoia Agent are my two go to psychological anime. Be warned they are disturbing, and not really romantic or yandere. But I really respect them as whoever made them clearly seemed to understand real madness.
It is one thing to say the character is an ax welding psychopath, because "hey they got an ax and someone said so". Versus the frighting yet subtle similarity to actual insane people you met while at a mental hospital when you were dealing with problems. It the old story telling telling vs showing, and showing is so much more powerful.