6. Peter Petrelli (Heroes)
It saddens me to put the once promising Milo Ventimiglia as Peter on this list. During the first season, Peter's potential as the leader of this group of unlikely heroes was in full swing. He began to collect incredible powers, displayed true heroism through his empathy (the source of his ability) and gave the series' unstoppable villain, Sylar, a worthy adversary. But then the world fell in love with Zachary Quinto as Sylar. He was a villain that we wanted to become a hero, and he was even teased as such. His incredible abilities and complicated motivations made us root for him without even feeling bad about it. Unfortunately for Milo, this put Peter in the backseat, and his character suffered. By later seasons, Peter was so stripped of his once enormous power that it hurt to watch him flail onscreen. It was quickly obvious that the meat of the character was pretty hollow if you took away his ability to actually be a force of change in the Heroes world. Looking back, it's almost impossible to find instances when he was a real asset after Season 1 (though it happened on occasion).