Well, how about this?

After his frustrating defeat, Infinite returns for revenge. This time, with the Phantom Ruby in full power, he decides to go after the heroes to put them in their place. As expected, he goes after Shadow first, but this time the jackal takes a less destructive and ostentatious approach and instead decides to test the limits of his magical gem, fueled by his imagination. He then decides to transform the Ultimate Life Form into a beautiful, stunning girl with no special powers beyond her beauty.

I would suggest that Shadow be transformed into a bimbo version of Vanilla, Rouge, or Amy. After his shapeshifting, he would try to fight regardless of his disadvantage, but then he would be brainwashed to adjust his personality to his new appearance.

The next victim would be Sonic, who would watch in disbelief as a defeated and transformed Shadow would be at Infinite's feet, worshipping him passionately.

a MtF of Sally Acorn by a machine or soemthing like that would be interesting