11 Most Terrifying Sci-Fi Movie Monsters
8. Monster From The Id - Forbidden Planet
Stretching all the way back in time to 1956, to a seminal sci-fi film that would go onto inspire Star Trek. This sci-fi adaptation of Shakespeare's The Tempest would pioneer many different aspects of the modern sci-fi movie; including faster-than-light travel, robots with a distinct personality and appearance, and of course, terrifying and incomprehensible monstrosities from beyond human existence.
The "Monster from the Id" as its called is an invisible psychic construct created as an inadvertent side effect of scientist Edward Morbius' use of an ancient alien civilization's technology to increase his own intellectual capacity. This Monster is constructed from the subconscious base desires of those who use the machine, given free rein and unlimited power to affect the material world. It's massive, invisible, and can't be killed by conventional means - impervious to any high-tech weapons the characters try to throw at it.
A single one of these creatures wiped out the entire alien civilization millennia ago, and it's been granted new sentience and new power by Pidgeon. Only Pidgeon himself is able to destroy what he created, and in the process winds up destroying not only the entire planet but everything within a 100 million mile radius. Jesus Christ 1956, you were hardcore.