While memorable movie monsters are usually relegated to the horror films, there are a number of deadly movie monsters within the sci-fi genre as well. There are some crossover monsters that could be considered both horror and science fiction creations, of course, so be sure to check out our look at the Deadliest Horror Movie Monsters as well to see what might have made the cut over there.
Science fiction monsters go back as far as horror films, with creature features and alien invader films filling theater seats since the dawn of the cinematic age. Just as science fiction has evolved alongside science, so have the movie monsters within the genre. This has created some incredibly deadly sci-fi monsters, as we're about to see.
10 THE BLOB
As a representative of the earliest science fiction film monsters, The Blob is a fantastic example of the kind of monsters that appeared in the early ages of film. 1958's The Blob introduced the slow-moving gelatinous form that constantly grows as it consumes terrified human beings.
1988's remake of the same name wasn't released to critical acclaim but developed a cult following, much like the first film. The effects of the remake increased the horror of the creature as it's acidic form painfully dissolved the citizens of a Colorado town. The Blob may be slow, but it is incredibly deadly.
9 "GORILLA-WOLF MOTHERF***ERS"
Joe Cornish's 2011 Attack the Block exists in a few genres as a science-fiction horror comedy, but still features some deadly alien creatures that aren't really given a name in the film, beyond "gorilla-wolf motherf***ers." It's an apt description of the creatures, as they share similar aspects of the two dangerous Earth-born creatures- with a twist.
The aliens in Attack the Block are pure black, making them almost impossible to see in the darkness (save for the luminescent glow of their razor-sharp teeth). Strength in numbers also applies in their case, as the race of creatures hunt en masse for their breeding mate throughout the film. Sure, a squad of kids from the block managed to take down the aliens, but that doesn't make them any less deadly.
Aliens may be some of the biggest threats in the science-fiction genre, but the other side of the coin are the monsters we create ourselves. We've always been the best creators of our own destruction, and our usual chosen destructor is not the Stay-Puft Marshmallow Man, but the robot.
RoboCop introduced the heroic titular cyborg, alongside the deadly and completely robotic ED-209 (which was full of firepower and faulty commands). Unfortunately, it lacked the programming (and stair-climbing ability) to really prove effective in the long run, but an army of ED-209's on flat ground is a force to be reckoned with.
7 INDOMINUS REX
It may seem rude at first to call dinosaurs "monsters," considering their origins on Earth as evolved creatures like the animals and humans of today. However, in 2015's Jurassic World, humans once again created the weapon of their own demise by splicing a number of deadly dinosaur genes together to create the Indominus Rex.
A mixture of T-Rex, raptor, and who knows what else created a monstrous dinosaur with a bloodlust, which could also camouflage itself in its surroundings. The Indominus Rex killed for fun after it broke free from captivity, and was the biggest and baddest monster around until a bigger and badder one showed up.
Also known as "Space Locusts" or simply "Aliens," the Harvesters appeared in 1996's Independence Day as they launched an attack on Earth and nearly wiped out humanity. Their origins, motivations, and abilities have been expanded upon in various other forms of media, but the initial film highlights what makes the Harvesters such a deadly threat to Earth.
While organically weak and defenseless, the Harvesters rely on their advanced technology. They have both personal protection in the form of biomechanical armor, and city-destroying ships full of smaller fighters that destroyed nearly every major city on Earth. Unfortunately, their technology also led to their downfall, just like the sequel led to the downfall of the franchise.
5 BODY SNATCHERS
When looking at deadly monsters, it's not always the ferocious creatures or dangerous robots that pose a serious threat to humanity. We've seen a few films based on Invasion of the Body Snatchers over the years, which is a testament to the horror of the "pod people."
The invading Body Snatchers are alien plant spores that almost perfectly replicate a human being, though they are left without emotions. In most film adaptations of the original novel The Body Snatchers, the ending is left ambiguous, with the implication that the invasion of the alien spores is never stopped, making them one deadly alien threat.
While classic Kaiju monsters like Godzilla may sit more comfortably in the horror movie realm at times, Guillermo del Toro's Pacific Rim introduced giant mechs to battle the monstrous creatures, further bringing the classic monsters into the science-fiction genre.
The gigantic creatures pushed humanity to the brink in the film, as Kaiju monsters like Knifehead were able to defeat the manmade Jaeger mechs. The Kaiju War led to the deaths of thousands and cemented the Kaiju as some of the deadliest monsters in any genre.
The ultimate example of human-killing robots are the aptly named Terminators, which first appeared in James Cameron's The Terminator and come in a number of different models, all constructed to specifically hunt down and kill humans.
The most well-known model is the T-800, which was covered in organic flesh in the shape of Arnold Schwarzenegger, to facilitate time travel. That one machine alone caused an absurd amount of damage, and the future is full of models that now surpass the T-800 in their terminating ability.
Also known simply as "bugs," the aliens from Starship Troopers come in a variety of forms that are all incredibly deadly. While there are huge artillery type bugs, it's the swarming attacking bugs that really devastate a planet's population.
Armored shells, acidic vomit, slashing claws, and a number of other dangerous adaptations seem to have specifically evolved in order to better combat the armies of humanity. Of course, while the alien Arachnids are very deadly, the real monsters of the franchise turn out to be the humans.
While we've discussed robots like ED-209 and the Terminators who bring massive destruction down upon humanity, it's the Machines from The Matrix that really lead the pack when it comes to destroying/enslaving humanity. Some of the other movie monsters on this list were stopped or failed in their attacks, but not so in the world of the Matrix.
Machines won, humans lost. Humanity was turned into a form of energy to help power the machines while their minds lived on in virtual reality. Humanity had to create a virtual reality figurehead to even begin to fight back in the war between man and machine, proving how deadly the Matrix is/was/will continue to be.