5. The Sixth Doctor's Attempted Murder of Peri
"Disagreeable" is a perfect term to describe the 6th Doctor's short tenure. A conscious rebellion against the rather placid and agreeable 5th Doctor, one of the first things the 6th Doctor utters is an insult aimed at his companion ("That's 3 I's in one breath, makes you a rather egotistical young lady.") From there, things get much, much worse. Unhinged by his regeneration, the Doctor becomes fixed on the irrational notion that Peri is actually an ancient, evil creature and physically assaults her, attempting to strangle her to death in the TARDIS control room, a scene that is still rather shocking to this day. I mean, can you imagine David Tennant stabbing Billie Piper? This is a scene that couldn't be done in the snug and comfy domestic atmosphere of the new series. Just to throw a little salt into the open wound, The Doctor then threatens to bring Peri with him to some desolate, solitary asteroid for a few decades while he gets his head straight. Lucky for Peri, the story kicks in at that point, saving her from that unimaginable fate. Unfortunately for the audience, that story is "The Twin Dilemma."