Surprised no one has said this, since they're in the same show but Rose Leslie (Ygritte in GoT) would have been a thousand times better than Sophie Turner.
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It would have been nice for Fox to grow some balls and cast an ethnically African actress as Storm, rather than a mixed-race actress, but alas that's Hollywood for you (and as someone touched upon upthread, Storm has never looked all the African; it's no wonder her hair is white with all the chemicals it must take to straighten it).
Tye Sheridan both looks like a boy scout and has a very punchable face, so spot on there as far as I'm concerned.