I like Tai Lung, as well as these other villainous animals:

Aeon the Terrible (Rudolph's Shiny New Year)

"Honest" John Worthington Foufellow & Gideon (Pinocchio)

January Q. Irontail (Here Comes Peter Cottontail)

Lotso (Toy Story 3)

Reginald (The Nuttiest Nutcracker)

The Terribly Deep Thinkers (In Search of Santa)

Vincent (Over the Hedge)