Originally Posted by The Guard
-Bane hates the rich...because he wasn't born rich.
-Bane, though we're never actually shown this, really wanted to be at Ra's Al Ghul's side, and resents Bruce for not wanting the same thing he did and working against the league.
-And Bane has an unwavering loyalty and love to Talia, and so he does what she wants.
Bane hates rich people because he wasn't born rich. Bane hates Bruce for not wanting to be a villain, and is...jealous of him? And Bane does whatever Talia wants because he loves her and is loyal to her.
Mind you, none of this is actually explored.
How is that not a thin character again?
Well no, it's not necessarily that he hates the rich because he was born with nothing and is jealous (though I would say he'd be jealous of Bruce getting picked by Ra's), it's that he loathes this idea that they think money can buy them power, when in his experience money has nothing to do with true strength and power. He's a leader that gets his hands dirty and puts himself out there with his men. That earns him the kind of respect and loyalty that's priceless, the kind Daggett wouldn't know a thing about. Couple that with the fact that he was living down in a hole until Ra's schooled him in the ways of the world, and you've got a fully indoctrinated ticking time bomb waiting to go off.
In short, I think the sum total of everything we learn about the character, while much of it is left off screen and for us to infer and interpret ourselves, leaves you with the impression of a complex man with his own epic journey through life, just like Bruce. Deeply evil, downright barbaric in a sense, but very deeply human too. In fact, Ra's felt like a much more fully fleshed out character too by the end of TDKR. I left that theater wishing there was a spin-off novel to read about Bane, Talia and Ra's...and that's a compliment.
So if Bane's primary weakness or thinness as a villain is that he is an extension of Ra's, so be it. I love Ra's as a character and loved the added dimension he gets in TDKR. It actually makes Batman Begins a better movie for me.