X appears to be Peter Leko.
Another odd one out

Oh, I can't believe I didn't see this one before!
XIII is Lasker of course!
Yes!

And IX is Max Euwe.
The odd man out is Short because he's never been World Champion. :[
EDIT - wait, Nimzowitsch hasn't been WC either. Hmm.
11/11 for Zank.