Joker is such, it has some twist, but good background story on vigilante police actions for crimes that might be difficult to go to court.
Nothing too unusual, too complex, not too outstanding even. But the cast saves this. Especially the character Sato (translate to real person?). He is so understated, so restrain, and so subtle. And that's why people call him Buddha That it works for the plot.
And the theme music, it is dramatic but makes up for the cases and the underlying anger within the main protagonist. It fits him to a T.