I don't pay much attention to lyrics unless I really like the song and to sing along and/or learn the subject matter but of the few artists who's lyrics I have paid attention to:
Ayumi Hamasaki: Easily one of the best not only in J-pop but in music period. Her pre-(miss) understand era lyrics were absolute poetry.
Hikaru Utada: This is awkward because I would actually put down Hikki in both the worst and best categories. Her Japanese lyrics as so beautiful, human, and have actually made me cry while her English ones are simplistic, awkward, and plain don't make sense.
Yasushi Akimoto: I don't know about any work he's done outside of AKB48 but he's done some bold and terrific work writing for this group with songs like Keibetsu Shiteita Aijō, Skirt, Hirari and Beginner touching subjects most idol producers wouldn't think of.
Yuki Kajuira: As well as being a brilliant composer, she writes some very beautiful, soothing, and powerful lyrics. And I love her Kajiuran language that though confusing, adds a unique touch and beauty to her songs.
Oh and Francis Lee's lyrics for alan's RED CLIFF made an already perfect song sung by a flawless vocalist into audio nirvana.
I honestly can't think of any "worst" out there for Asian artists. There's been some unimpressive, meh, or things intentionally meant to be hilarious and wacky but nothing I would consider the worst ever but again, that's probably due to me not paying too much attention. For Western artists though... yeah, I can name a few. One of which has already been mentioned.