In terms of how much I like them;
1. Icy
2. Stormy
3. Darcy
4. Selina
In terms of how good they were as a villain;
1. Icy - I think she's a great determined leader. She very smart and has a good deal of power on her side. I wrote an article on this once.
2. Darcy - Very smart and very mature. Also has great powers.
3. Stormy - Though she's got a lot of power I put her at 3 because she is very impulsive.
4. Selina - I have nothing against her but based on the few episodes I watched of season 6 she pretty much seemed to just follow orders.