Frederick is currently Level 5 in my over 40 hour playthrough. And he's still a Great Knight.
He's actually a pretty cool character, but at this point he's pretty much one of the weakest people in my army. I guess that's what happens when you rarely use someone. --- Ah, yes, the Negotiator: General Kenobi <sneaky beeping>
All these people talking about Frederick must never have played a Fire Emblem game before, every single one has an already promoted knight of some kind at the beginning that tears through everything that so much as looks at you sideways, but is a massive waste of xp to actually use.
Problem is that this game actually made him necessary in Lunatic D: --- http://i.minus.com/i6KFWnapcCjuP.gif