Challenge Mode was B/W 2 only, and it was more challenging than the regular game, especially the first half. The second half was still fairly easy though. Problem is that you had to either beat the game once or transfer the key from someone else's game to unlock it.
And Honedge's final evolution absolutely kicks ass, so you'll have a blast with him.
And Honedge's final evolution absolutely kicks ass, so you'll have a blast with him.