Some if these have already been mentioned but:
Love Pandora, Endora, Eudora, Isadora and Theodora, hate Dora.
Love August, hate Gus (but like Auggie(-ish))
Love Edmund, hate Ed, Eddie etc.
Love Caspian, hate Cass.
Love Isadora and Isobel, hate Izzy.
Love Finn, hate Finn- anything, especially Finnegan.
Quite like Sebastian, hate Seb.
Quite like Nathaniel, hate Nate (haha) and Nathan.
Love Benedict, Benoit, Bennet, and Benjamin, hate Ben.
Love Alexander, hate Alex (Xander's okay)
Most of the time it's the nicknames I don't like. Loads of them are associated with other more popular names, and I don't see the point of having a more unusual full name. Especially with nns like Izzy, most people would think Isabelle (or some variation), not Isadora. (Gish I can ramble :P)
I like Elizabeth, but dislike the most common nicknames (Liza, Libby, Beth, Elle).
I like Pippi and Poppy, but not Penelope.
Those are the strongest ones, but with most of the long names I like, there's an unwanted nickname with the exception of two: I like Maelie for Maelys, and Will and Liam for William.