[He probably could wish him dead, actually, but that takes the fun out of it.]

I'd much rather watch him squirm as I take control of the whole Mushroom Kingdom. With the Star Rod in my clutches, only my wishes will come true, leaving those poor, pitiful citizens without hope. They'll wish their hearts out and find it doesn't matter!

And no matter how hard he tries, Mario will be left powerless, unable to free the Star Spirits, unable to whisk Peach away for the billionth time!