While I really enjoyed Tom Hiddleston as Loki, I just don't see him as one of the 20 greatest movie villains of all time, certainly not #3. I think they try to portray him too often as kinda sorta good, a little misunderstood and in need of guidance. That's not to say that he hasn't done villainous things, of course; I mean, in the first Avengers movie, the guy committed cold blooded murder and orchestrated an alien invasion that he kinda sorta regretted after he saw the devastation that was being caused. Loki's just not dark or depraved enough in my opinion.
I'd have put Nurse Ratched from One Flew Over the Cuckoo's Nest higher on the list. She was such a cold hearted, merciless, uncaring tyrant who delighted in controlling every aspect of the lives of people suffering from mental illness. If possible, she relished seeing the struggles they had to endure just as much as the control and was positively glowing when she dispensed punishment.
Palpatine definitely should be higher on the list. I mean...hell, the man was so butt fuckin' evil that he orchestrated an interstellar war that untold numbers of beings.
"What Do I Know Of Cultured Ways, The Gilt, The Craft And The Lie?
I, Who Was Born In A Naked Land And Bred In The Open Sky.
The Subtle Tongue, The Sophist Guile, They Fail When The Broadswords Sing.
Rush In And Die Dogs - I Was A Man Before I Was King."
Conan Of Cimmeria