Katherine, I think is a stunner. I feel weird saying that since it’s basically just the English version of my own name but I think it’s a legitimally gorgeous classic.
Catherine and
Katharine are just as nice.
Katie on its own is okay. I like it as a nn but as a stand alone name, it’s a little underwhelming. Still nice, though, but it’s better as a nn for
Katherine,
Kate,
Katharina, etc.