The bulk of his portrayal attributes his being a dick directly to his issues with Magneto, culminating ultimately in House of M where he uses his own sister to give his daddy the gift of power.Quicksilver is great. He's a complete and total dick because all he wants to do is go 700 miles per hour at all times and everyone he knows mooooooooooooves sooooooooooooooooooooo sloooooooooooooooooow. I remember one line in an old comic where he described his life as being eternally in the slowest line of the DMV.