The latest hero of the time-travel adventure series Doctor Who, David Tennant, claims at one point that he "used to have so much mercy." Which started us wondering: When was that exactly? When he condemned his former best friend to a fiery death while the friend (the Master) begged to be saved? Or was it when he consigned the mad scientist Davros to 90 years in suspended animation, with Davros conscious for every horrifying second of it? Watch our compilation of the Doctor's greatest acts of "mercy" from the classic series, and decide for yourself. (Background music is the disco Doctor Who theme, by Mankind.)