Re: Which characters "stand out" for having been completely ignored throughout Naruto
Tenten. The only difference between her and the fodders you see in the background is the former has a name and the latter doesn’t. She’s as relevant as them; irrelevant.
Re: Which characters "stand out" for having been completely ignored throughout Naruto
Shino and TenTen got the worst of it. At least Kiba was a part of the Sasuke retrieval team in part 1. Honorable mention to Sai for that moment when Sasuke comes back during the war and Naruto effectively shits on their bond and casts him aside.
Re: Which characters "stand out" for having been completely ignored throughout Naruto
Goddess Tenten, she has roughly 1 fight in the entire manga, that being temari which wasn't even shown. Her potential character development got passed to Sakura, and then her chance to shine in the war was completely forgotten/ignored.
Re: Which characters "stand out" for having been completely ignored throughout Naruto
Pretty much every member of Akatsuki save for Obito, Pain, Zetsu, and Itachi. Once they were dead, their impact on the plot was minimal until they got revived basically just so they could die again.