Overrated:
Nagato - people actually think he could beat Madara or itachi, wich is bullshit.
Naruto - people think he's able to defeat Madara
Sasuke - Seriously, he only wins because his team mates keep healing and protecting him.
Orochimaru - People think he actually poses a threat, with the current ninja, he's far out of his league.
Jiraiya - People think he could defeat Itachi, wich is also bullshit.
Minato - He's strong, I admit that, but no, he's not as unbeatable as fans make him out to be.
Kabuto - Because he summoned Madara.
Tsunade - lately I've seen people saying she's not completely worthless.
Underrated
Kakashi - Since he got skilled with his MS he can basically one shot anything.
Kisame - all he had was a bad matchup, and he even survived the afternoon tiger.
Itachi - he's more underrated than overrated, he can't defeat someone like Madara, but he IS better than Jiraiya or Nagato, period.
Neji - he's the best byakugan user out there, and the only jonin in the k11, yet people think others from the k11 could beat him.
Tobi - he was hyped up to be a weaker than expected, but on the other hand, without kakashi he's close to invincible.
Konan - she did more damage to Tobi than anyone has done so far, that move would've killed even Pain.
Tenten - I actually think she has more use than lets say...Sakura or Hinata.
Danzou - He would probably have killed Sasuke if it was'nt for Karins help and Danzou having to pay attention to Tobi not interfering all the time.