Dum Dum Dugan can't really be a character since Captain America was sleeping for 70 years in this canon (if he's not dead he's ancient now). I only recently saw it too and it's a pretty fantastic movie. I think we could have used a SHIELD movie or something that just showed Nick, Black Widow, and Hawkeye doing things, but that probably wouldn't have the same appeal to casual movie goers as the other Avengers have. My only real complaint was that the Chitauri could have used a more present leader since Loki wasn't officially their commander or anything (though I know nothing about them in the comics, so it may not have made much sense anyway and inventing a character always serves to piss off hardcore fans).
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