@ariella- Funny enough, I thought the most sympathetic character in Avengers was Ultron. Tony Stark was a paranoid fool. Captain America had reduced his humanity to just being a soldier which means he's next to screw up. Black Widow wanted out. Thor has always just been a caricature. Hulk just smahes. Ultron was trying to remake the world as a better place as he saw it rather than trying to keep it from changing.
In the end, of course, he's wrong. But like all good bad guys his motivations were understandable.
Funny enough, that sort of "human" AI is what studies show might be more trustworthy. Granted, without the evil part. :)