I can see Scorpion working for someone at first and then turning against those who made him, becoming a villain with his own agenda.
I'd rather they not go down the whole revenge angle with Scorpion. Too often it's forgotten that the guy's completely nuts. And why is that? The experiment? I don't think so. A man doesn't simply go insane over night.
Rather, I think it would be far more interesting to show Gargan's growing depravity. He was a hired sneak, a paid snitch, he followed people, rummaged through the gutters and made a pittance. He was a nobody, only defined by the sins of others.
Given that background of sleaze, I think it would be interesting to play it up. Have him be a grotesque, oafish slob. Not like a typical
Noo Yoik thug as some comics protray him as, but rather like a bloated glutton or alcoholic.
The transformation didn't change his seedy persona, all it did was remove his inhibitions. Someone like that can be very dangerous when given a little power, because they lack even the most rudimentary of moral constraints.
And slowly, after he's indulged in vice after vice, he could well become someone you would class as being truly insane.