I never thought any Indy villians were scary either really.
Cate did say in a brief interview, she relished the part of Irina, she said the part of Irina was "a villian, with a campy wink in a storybook world".
Mola Ram, is probably the evilest, but I think Spalko was really good. I am sure if the movie was darker, they'd have made her even darker she had the potential to be darker, with her psychic power. One of the best scenes is when she is telling Indy of their plans with the skull as he stares in to it.
And I agree Agent Z, she got a lot more involved in the movie than most villians and I think she was very likeable! I, and a few more people I know, were sad to see her death!
She had potential to be a dark villian, they just decided not to make her one. I still really like Irina Spalko though. She worked with Indy, and she wasn't really an evil person anyway - she just wanted to acquire a higher knowledge of life, and literally died for it! Also, it is true, out of the Indy major villans she is the only one that really got her hands dirty. Mola Ram put up a good fight on the bridge though!
Also, yes, the scene where she was hanging on the turret gun, I was glad to see that. I thought it was really fun to see. As sophisticated and cold as she could be, it was great to see her thrown in to obscure and comical situations (like the ants). Even though I didn't like the monkey swing, (or know why monkeys would attack her), I must admit, the moment one runs over her chest and face as she leans back to try and avoid it, makes me laugh!
As for Donovan, I quite liked him.