At first, Polnareff believes him to be a complete idiot, since Devo was hiding in the fridge of Polnareff's room and left all the drinks outside, above the very fridge, making himself easily detectable. However, that was part of Devo's plan, as he intended to be detected by Polnareff and hit by his Stand to activate his anger.

He is also extremely sadomasochistic, taking blows with ecstastic joy, while planning to kill his victims in brutal ways. Through the control of his doll, he becomes even more psychotic and perverse.

You can put your own spin on it!