Doctor Who: 15 Greatest NuWho Deaths So Far

Another character that took their own life was Adelaide Brooke. Destined to die on Bowie Base One on Mars after the base is attacked by the parasitic Flood, she is saved from her fate by the Tenth Doctor, at this point getting drunk on the power and his decision that the rules of time are his to control. Recognising the monster he is becoming, and the potential havoc her survival could reek on the future development of the human race, she  subsequently commits suicide by shooting herself with a laser gun.

The sudden shock of Adelaide's death stops the Time Lord in his tracks, as he realises he's gone too far, and it's just as shocking for the audience. This is the point in the episode where everyone has usually been saved, after all, and Adelaide has been a strong and entertaining character. The death was unexpected, so it hit harder.

It's alos a heroic sacrifice. Adelaide's death ensures that human history stays on course, and prevents a power-crazy Time Lord from trying to reshape the universe. As such, she valiantly sacrifices herself for the greater good.