Sivana
Here he is, Thaddeus Bodog Sivana!   Sivana is built on a Robin base with a Mr. Freeze head.  I used Robin because he is the shortest of the Super Powers line.  He also has a bit of a hunch back which is good for this custom.  I modified the Mr. Freeze head by adding a bit of cranium to the back of the head.  I sculpted the lab coat out of Sculpey, and also added pants with Sculpey.  I then primed and painted the figure.