(Photo: BBC America) 
When it comes to the Doctor’s worst foes, most of them can be said to have motivation that is broadly understandable. The Cybermen want to fix everyone. Sontarans just love fighting. But there are some interstellar swine whose reasons for doing what they are doing are harder to comprehend. Or forgive.
Let’s put it this way, we’ve all felt a little Pting from time to time, but it’s tougher to empathize with a tin dustbin that keeps trying to shoot everyone, even on a bad day.
Here are some other of the Doctor’s enemies whose motivations are just plain rotten:
1. The Carrionites (“The Shakespeare Code”)

Creepy from the word go, the Carrionites were so unpleasant that even Time Lords kept out of their way. And let’s look at the special powers bequeathed by their word magic to the three witchy women who came to terrorize Shakespearian London. Mother Doomfinger (not a friendly name) can kill people with a single touch, Mother Bloodtide (from the Red Sea, probably) can fly, and Lilith (the one with the nice name) can kill with a voodoo doll. And what do these creepy people want? To wipe out humanity and establish the “Millenium of Blood” on Earth. Lovely.
2. Krasko (“Rosa”)

Never mind the fact that he looks like George Michael in 1950s Alabama, the thing that makes Krasko such an unsympathetic baddy is that he’s a fascist. Not a clever parody of the most extreme moments of Nazi ideology, like the Daleks are, but just a common-or-garden mass murdering British white supremacist with a modern day beard, a neural inhibitor preventing him from doing any more murders, and a Fonz fixation. Never mind time travel, he belongs on the internet.
3. The Bannermen (“Delta and the Bannermen”)

Well the Bannermen are just the worst. They polluted their home planet until it became unlivable, then attacked the peaceful planet Chumeria in order to colonize it, killing all but one of its inhabitants, the Chumerian queen Delta, who ran away with  her egg. Not being able to enjoy the fruits of their own awfulness, they gave chase, winding up in 1959 Disneyland and that’s where they encountered the Seventh Doctor. Had they just been a bit more careful with litter and gas emissions in the first place, none of this needed to happen. You just can’t teach some people.
4. The Zygons (“Terror of the Zygons”)

When you stop and think about it, aside from the fact that they look scary, and gross — at least in their undisguised form — Zygons are a very inscrutable species. Oh sure, once they’ve invaded a place and had to disguise themselves in order to fit in, it’s pretty clear what their motivations are. It’s your average evil villain mindset. But why are they like that? How do you evolve the unique Zygon combination of squid-like physique, poison sacs under the tongue, and the ability to shapeshift?
Is this the result of millennia of extremely cautious breeding, in which your crush might turn out to be someone completely different, and venomous to boot? Is romantic diplomacy a much bigger consideration for them than us? And most importantly, if you could choose to look like anything in the universe, why would you choose to look like that?
5. The Zolfa-Thurans (“Meglos”)

Unlikely things are ten a penny in Doctor Who. So it shouldn’t be that surprising to hear about a six-foot tall sentient cactus being able to communicate telepathically with humans. Or that said cacti had also developed the technology to transform their personality into other life forms, then ride them around until the re-cactus-ification of their host. Or that, having discovered that he is the last of his race, following a global catastrophe, the Zolfa-Thuran criminal known as Meglos should seek to grab his people’s most potent weapon — a galaxy-threatening device called the dodecahedron — and use it to try and gain power.
No, the real head-scratcher here is how on earth a no-handed cactus developed this superior technology in the first place, when humans (with our wonderfully dexterous fingers) can’t even manage to invent a self-cleaning bathtub.
6. The Grand Serpent (“Once, Upon Time”)

There’s no question that this fellow is a rotter. He’s cold and imperious, he exiles Vinder to a remote space sentry point just for questioning his judgement and (this is the kicker) he shares his body with a snakey creature that kills people he doesn’t like. What we don’t know is why he is like this.
Once upon a time, the being known as the Grand Serpent was what he calls a “beloved leader” and then, at some undisclosed time after that, he was deposed. We don’t know why, but after that, he started scheming. He schemed his way into shutting down UNIT. He schemed his way into an alliance with the Sontarans. But other than the fact that snakes are gonna snake (snake snake snake snake), we’re just left with another English-accented baddie being imperious and cold because he can.
7. The Mighty Jagrafess of the Holy Hadrojassic Maxarodenfoe (“The Long Game”)

The Jagrafess is a sentient slug thing, which looked like some kind of medical prolapse, could only talk in growls and howls and had to be kept really cool at all times, for fear of spontaneous explosion. Granted, this description could also apply to any number of ego-fevered television presenters, but within Doctor Who, this particular snotgoblin ruled the Fourth Great and Bountiful Human Empire as a puppet of the equally bogey-armed Dalek Emperor. 
Sadly, we do not know how the Dalek Emperor came to recruit the Jagrafess in the first place, and we do not know what it thought it was doing and what it wanted out of life.
8. The Whisper Men (“The Name of the Doctor”)

Where do these emaciated zombie gentleman ghost-geezers even come from? And why must they quote poetry all the time? Are they just cyphers and products of the fevered imagination of the Great Intelligence? And if so, do they just vanish when he forgets about them? Don’t they have their own lives? Loves? Dreams? It seems not.
Creepy though they are, you can’t escape the feeling that, for the Great Intelligence at least, the Whispermen are just stage dressing with teeth.
9. The Sandmen (“Sleep No More”)

Given what the last few years have been like, it’s very hard to establish a sympathetic response to a Doctor Who villain that is essentially a sentient virus. The Sandmen are eye-boogers made monstrous; a carnivorous lifeform not unlike the Vashta Nerada only blind and lumpy and looking to hunt down tired people and convert them.
Sure, you can sort of see why an infection might feel the need to spread out, but taking the part of the virus against the people it infects is the sort of thing only the more rabid end of social media would consider to be the correct empathic choice.
Do you have any theories on what makes these baddies so bad?