And because, in all the Galaxy, they had found nothing more precious than Mind, they encouraged its dawning everywhere. They became farmers in the fields of stars; they sowed, and sometimes they reaped. And sometimes, dispassionately, they had to weed.
The Predators in general. They are a species focused on the hunt, and all of what we see of their culture and technology is obsessively focused towards hunting in all of its forms. The only time we see a Predator engaged in an activity other than hunting is in Requiem, which has a shaky place in the Aliens/Predator canon.
The Cenobites in Hellraiser start off this way. They are described as "Hell's referee", an emotionless force that fulfills their function with no real human concept of right or wrong. They don't distinguish between pleasure and pain, and they don't think too hard about what they're doing in human terms. "You opened the box, we came." End of discussion. As the sequels went on, Pinhead became overtly villainous.
The Martians in Mars Attacks! declare war, apparently, because they see a bird; laugh, cry and get angry for reasons incomprehensible to humans; cut off someone's head and keep it alive for no apparent reason; put another person's head on a chihuahua's body, again for no apparent reason; and their language consists of the word "Ack!"
Leek: You're asking for an explanation for something that can't be explained rationally. You know the buildup of energy before something happens? The way your hair stands up before lightning strikes?
John: "Before something happens." Do you mean they cause disasters?
Leek: Why would they need to?
John: All right, then, are they trying to warn me?
Leek: Their motivations aren't human.
John: All right, then what do they want?
Leek: I have no idea. What you really want is to know: why you?
Leek: You noticed them, and they noticed that you noticed them.
Anton Chigurh from No Country for Old Men is described as having a set of rules that make sense to nobody but him. You get some small idea of his moral code in the gas station scene early on in the film where the store manager tries to make light conversation with him. It's revealed that the manager married the daughter of the former owner of the premises and this visibly irritates Chigurh ("You married into it"). He forces the shop owner to flip a coin to save his life for no exact reason. Later, when he makes good on his promise to kill the main character's wife, he allows her the same coin flip to save her life. She tries to argue with him, but doesn't seem to get anywhere.
Most non-human creatures in Prometheus. Engineers had a hand in creating humans and human culture, but also attempt to kill them whenever they come face to face. Trying to figure out their reasons is one of the mysteries of the film. Also, David's morality is ambiguous. He seems to value knowledge above all else and will place human lives in jeopardy to satisfy his curiosity. If you read between the lines, David's using the Engineer goo on Holloway may have been, in his mind, sanctioned by Wayland, who did tell him to "try harder." Looked at in a certain way, he does even get a kind of informed consent, asking "what would you do for the answers you seek," and taking the reply of "anything" as permission to proceed. Still rather Blue and Orange when compared to regular human ethics, though.
Jeff Bridges plays a very disturbing serial killer in a little known 1993 remake of a 1988 Dutch film called The Vanishing. In the film, he describes how he saved his daughter from drowning, believing that this act earned her adoration. He then decides that he is unworthy of his daughter's love unless he proves to be capable of performing an equal act of evil.
The Mi-Go from the 2011 adaptation of The Whisperer in Darkness are a classic example, in line with what Lovecraft originally had in mind. After Wilmarth, the protagonist, thwarts their plan to open a mystical portal from Yuggoth (read: Pluto) to Earth, and then crashes a plane into the ritual site for good measure, they actually go out of their way to save his brain, place it into one of their cylinders and take him around the cosmos on incredible adventures. Even though he had foiled a plan that had likely been in the works for several centuries, and despite the fact that they said he was unworthy of being anything more that a sacrifice earlier in the film. Their minds work very differently, it seems. They're also repeatedly stated to be Consummate Liars. Another, earlier scene has Wilmarth stumble into one that was on its way to the ritual. The Mi-Go simply kicks Wilmarth out of its way and pays no more attention to him, nor does it inform its buddies of his presence. Had it done so, the ritual would not have been foiled in the first place.
In The Whole Nine Yards, Jimmy Tudeski is an Affably EvilProfessional Killer whose morals only occasionally approach anything resembling conventional morality. He'll threaten a waiter with bloody murder for putting mayo on a burger, play mind games with his depressed dentist friend, kill half a dozen people without batting an eye, and murder his helpless wife to become the sole inheritor to a Tontine… but he won't let his wife divorce him and write herself out of the tontine because divorce is a sin. He gets around this by faking his death, thereby allowing her to move on with Oz without the sin of divorce. She knows he's only faking, but it still makes sense to Jimmy.