Ah, evil Griphook, the lover of all things gold and expensive. Griphook's betrayal of Ron, Harry and Hermione in the Gringotts bank caves (if only Barclays buildings were as much fun) is a serious one, despite the fact that they still find the Hufflepuff Cup and destroy it. Griphook's mistrust of wizards is no excuse for his possession over the sword, or him calling to the bank staff that there are thieves in the vaults. Well, he messed up entirely there, didn't he? The trio escape on a dragon, Griphook is called to Malfoy Manor to explain what happened, and Voldemort kills him with a killing curse. So really he got what all traitors deserve.