[TacitMike]

A royal flush or straight flush beats him. The reason I would argue he has the third and not the fourth is that the of three hands that beat him (QQ, ATdd, T9dd), only two are possible (if someone has ATdd someone else cannot have T9dd).

Edit: I guess the clarification (between third and fourth) depends on whether you consider the nuts the best possible hand considering the board (out of ALL possible hands) or the best possible hand currently involved in the hand (terribly worded, I know, but hopefully understandable).