I think these are all quite good! I don't know that I have any concrit to give as you are very good at seeing improvements in your own work.

I also like the comics style in the first one. I think it works really well! I love the top of the hair, the way you left it without pigment. I am bad about not leaving those areas, so I love to see people use them well!

Ginny's expression in the second is great. I also like her stockings quite a bit, as they remind me of the Wicked Witch of the West. lol

The white area between Snape and the background in the third draws my eye to him immediately. I love that contrast! You really use negative space so well.