One Fist's special ability is :

One Fist only has one hand for the purposes of equipping items. He may always make one Melee attack, rolling 1 Red and 1 Green die, in addition to his normal action.

Now my question is that when he makes this attack does he use the power dice as well.

It is a melee attack and hence subject to all the normal rules with melee attacks.

In short, yes it should include his power dice.

One thing to note, however, is that unless he gets an "other" item or something that allows him to spend surges, all surges on this attack will be wasted.