Deidara; he got hit by some stupidly easy attacks to dodge by Sasuke and Sasuke's Sharingan pretty much nullified most of Deidara's attacks...maybe not the MOST unfair in the manga, but pretty close I think.
definitely tenten--most awesome female and kishi makes her a filler...
haku and zabuza--best characters and dont get enough screen time.
diedara--lets face it sasuke was a piece of garbage, diedara's death it a plot hole
Sasori and Nagato. Sasori really got sold short in his fight, he gave up and gave away intel, wtf. Nagato had Naruto exactly where he wanted him but got tnj by Naruto and ended up sacrificing himself to revive everyone he killed. Orochimaru was also unlucky.
anyone naruto grew up with that isnt in his team from konoha. Definitly garaa because he lost shukaku and such. Sasuke because to progress the story kishimoto always throws some bs in which makes him seem weak which he isnt. Itachi because he died so damn early and now hes literally back and in full controll thanks to him being a broken character in naruto. Alot of stuff in naruto is pretty mixed/messed up honestly but its still a great story.
ALL of the hokages except tsunade. ( not enough stage time)
ALL legends ( legend of the 7 swords men, sage of six path, the beasts themselves etc)
naruto is hurt the most due to plot no jutsu
cuz he is not considered the main character of his own show
people go talking about madara , itachi , minato , sasuke , hashirama , like these are the main characters .