Helen Slater's Supergirl, I never liked Supegirl much because I thought Superman should be the only survivor of Krypton other than a few villains. But she truly is so beautiful like an angel to look upon, still the most gorgeous superheroine I've seen on screen. If only she could get a good script, man.
Antje Traue's Faora, she is so beautiful, strong, tough and powerful. That's everything a lethal Superman villain needs. I even became a fan of the actress. You can see Faora in comics started to base the image on her after MoS.
Quite a few Spider-Man villains, especially Jake Gyllenhaal's Mysterio, he was so charming in a deadly way, and Alfred Molina as Dr Octopus since he was quite sympathetic .