Doctor Who: 10 Defining Tenth Doctor Moments
3. Time Lord Victorious (The Waters Of Mars)
"For a long time now, I thought I was just a survivor, but I'm not. I'm the winner. That's who I am. A Time Lord victorious."
What viewers can often forget when watching his heroics on a weekly basis is that the Doctor can be an intimidating figure; he's not perfect and has the ability to stop those he disagrees with - often fatally. He's often bound by rules, but there are times he forgets them, and this is one of those. With the Flood bearing down and with a fixed point in time to contend with, the Tenth Doctor attempts to bend the laws of Time to his will.
As a result, he becomes drunk on power, claiming himself to be the Time Lord Victorious, and suggesting that he could mould events to how he wants to see them as the Last of the Time Lords. The shock that Adelaide's suicide brings him back down to Earth, but it's a look at what the Doctor could be as a villain.
It's a terrifying turn from Tennant, twisiting the Doctor's heroism into something altogether darker, creating one of Ten's darkest points. A lot of fans were disappointed that the last story of Ten's era didn't continue in this vein, which shows just how powerful this moment managed to be.