8. “The End of Time”
Although the new series of Doctor Who has been pretty solid as a whole, "The End of Time" is easily the biggest disappointment of the show. The entire two-part special is a mess, with very little to redeem itself other than Bernard Cribbins and Tennant himself. And what's with that whole "Hey I'm dying let's go spy on all my old companions for a minute here" thing? It’s overly sentimental and just ridiculous. Tennant was a very good Doctor but "The End of Time" is one of the worst regeneration episodes of all.