Willie from Romeo x Juliet should have become the main protagonist and the had the entire series devoted to him, undergoing the title change to, Willie: The Most Awesome Flamboyant Playwright Stereotype Ever.
Would have saved the series from mediocrity and propelled it into Greatness with a capital G.
Tenten from Naruto - heck, her chunin exam fight was SKIPPED in the manga, and that's all she's ever really got. She really needs to be in the series more. Kishimoto must just not like her or something.
But the series was Gonzo-fied -- even Gankutsuou didn't avoid that fate.Romeo x Juliet was greatness anyway....If anything, I think Francisco and Curio could have done with a bit more, however, the point of the series (and the original play) was the tragic love of Romeo and Juliet, which I feel was portrayed really well.
I would say Mori from Ouran. Very little dev in the manga OR anime
Well I would like to see Sado(Chad) from Bleach get some more attention. I feel that he has been left behind from the story, although he has been playing a bigger role latley. I just feel that he could have a even bigger role