While Altair and Ezio may have had their negative qualities, neither can match the petulance of Connor from Assassin's Creed III. He's far more of an outsider than the previous two heroes and while that might make him a more interesting protagonist (especially as an assassin is perhaps best left to his own devices), it actually drives much more of a wedge between the audience and him. Any interaction that Connor has with pretty much anybody leaves us with a thoroughly negative impression of the guy. Yes, he's from a Native American tribe (a destroyed one, to top it off) and having to adapt to a new way of life, but there's very little to like about Connor's personality. It's clear that Ubisoft wanted a "deep and brooding" protagonist to explore the events of the American Revolution but the dominant personalities of the other characters (most notably, the villains) overshadow him and make him almost irrelevant in his own story. It's hard to root for a guy who's so entangled in his own mind that he refuses to let his personality shine through. The odds are stacked against Connor from the beginning though. Ubisoft took a risk in Assassin's Creed III and forced us to play through the opening hours of the game with Haytham Kenway; Connor's father who eventually becomes one of the game's main antagonists. Not only is Kenway a more interesting character (as with most villains in games, his flair is allowed to shine every time he's on screen), the opening section only makes us want to play as the assassin we know is the leading role, thanks to E3 press conferences and trailers. When we finally switch to Connor and have to play hide and seek in the forest, it quickly grows tedious. Sorry Connor; Ubisoft simply didn't let you become the character you needed to.
I have an addiction to achievements, a craving for new bands and a dream to become Captain America. I once finished second in a Mario Kart 7 tournament so I'm kind of a big deal.