What's The Most Evil Villain You Have Ever Seen?

For Me It's Syndrome From The Incredibles 1,He Killed Dozens Of Supers With His Omnidroid, He Did Not Care If He Killed Kids, And Even Didn't Care When Mr.Incredible Tried Breaking Mirage's Back

Best left unsaid as to why.

Alternatively I could put just about any other warhammer character such as my goat Talos Valcoran.

Furthermore, Radec and Visari from Killzone (specifically 2) could be quite high contenders, if we exclude warhammer.