Dedede only uses two buttons, (X) and (Y). The former involves a hammer swing attack, and in the latter, it swing its hammer three times. These are Dedede's only two moves, and are the same when crouching or in the air.
That being said, Dedede's gameplay is very poor. Neither of Dedede's two attacks combo at all. Not even infinites are present, as its corner push is rather strong.