RIse of the Phoenixes - my favorite strong FL, it's serious, moving and worth watching although last episodes are rather rushed and messy
NIrvana in Fire - all was probably said about this one, my No 1 of this kind of dramas ; this is male leas drama but two main female characters are both awsome
Royal Nirvana - (watching it now) it's not only serious, psychologically nuanced, it's downright depressing but at the same time really, really good - that is if you can stand all the pain the characters go through; great visuals