Doctor Who: EVERY NuWho Villain And Monster Ranked Worst To Best

The Doctor's very own bespoke psychopath is at full Evil River tilt in Series 6's Let's Kill Hitler. She successfully poisons the Doctor with a kiss of death which also, significantly, disables his ability to regenerate. Unlike when River "murders" her husband on Lake Silencio, this River sheds no tears and instead barrels through 1939 Berlin brilliantly enraging Nazi soldiers and ordering people at gunpoint to take off their clothes because, you know, every newly-regenerated Proto-Time Lord needs a new look.

So what changed? Well, all it took was a combination of a dying Doctor whispering something in River's ear and Amy convincing her daughter that a now-dead Doctor was worth saving, so she sacrifices all of her remaining regenerations to resurrect him, and this time gives him a kiss of life to boot. Dear God, River is hard work young.