I have to go with Donyell. He may have been the most complete player when he left the program. I think a lot of people remember him mostly laying with LeBron in Cleveland and he had a lot of mileage on him. There was nothing he couldn't do in college (except those 2 freethrows).
Butler, is second for me, but he wasn't the force Donyell was underneath. Imagine having two Donyells under the basket... either end. He was a force on defense and the best finisher around the rim that has played at UConn. His size and freakish length were tough to match.
This day and age, hardly any teams press so he would be alright getting the ball up the floor on offense. There is enough handle there. The rest wouldn't be a problem, but just a matchup nightmare for other teams. He had the three, mid-range, back to the basket game, and would make the extra pass when it was there.
He, Ray and Doron together were so much fun to watch.