Excellent movie. Both the original with Robert Mitchium and the remake with DeNiro.
But DeNiro's Max Cady was much more scary.
Both were excellent films, and both Mitchum and Robert De Niro portrayed Cady very well. But De Niro's Cady was a virtually unstoppable and vicious psychopath.
Other favorite villains:
Hannibal Lecter
Dennis Hopper's character in Blue Velvet
Francis Dolarhyde from the movie Manhunter
Jason Voorhees
Jame Gumb
Scorpio from Dirty Harry
Little Bill from Unforgiven
Harry Powell from Night of the Hunter
I'll think of more soon...