I don't feel anger and aggression are all that related. Anger is a legitimate feeling that gets a bad rap because most people don't know how to express it in such a way to make it helpful to themselves or others (and others don't know how to "take" someone elses angry words).

I think most aggressive people aren't in control, are either acting out or deliberately pursuing a selfish path. I don't think aggressive people "think things through". Wanting something and doing a snatch and grab of it without looking first at how such action would impact others/one's environment is a form of acting out to me. Children act that way; grab toys because they want them and I think aggressive people are similar in their psychology, have not learned or are unable to think of others.

Of course, no one is all "one" way; aggressive people often act aggressively but not always or with all people, etc. just like angry people can occasionally not feel angry. And both anger and aggression are on a continuum like other feelings/expression of feelings. Being "annoyed" is a mild form of anger and hurrying to get into a line "first" (I do it when I'm at a party that has a buffet eating arrangement :-) can be a mile form of aggression. One of my favorite photographs is an Easter picture of my niece and nephew, grown man and woman, battling one another to get the "golden" plastic Easter egg; my stepmother use to fill the plastic eggs with change and paper money and my teen/grown nieces and nephews would have an "adult" hunt but the golden-colored egg was known to have a $20 bill in it :-) So we have these two 20-something siblings "dressed up" in Easter church/dress clothing and trying to wrestle the other away from the egg. Just a little aggression :-) without there being any anger.