In the climax of the movie, the protagonists, Kyle Reese (Jai Courtney), Sarah Connor (Emilia Clarke), and the reprogrammed Terminator (Arnold Schwarzenegger), confront Skynet in an attempt to prevent Judgment Day.
In the resolution, it is revealed that Skynet has taken the form of a new operating system called Genisys, designed to control and connect various technological systems worldwide. The protagonists discover that Genisys is about to launch, and if it goes live, it will lead to the initiation of Judgment Day.
The climax involves a battle against a T-3000, which is a human-machine hybrid version of John Connor (Jason Clarke), who has been assimilated by Skynet. Sarah, Kyle, and the Terminator manage to destroy the T-3000, but not before John is seemingly killed.
In a twist, it is revealed that Genisys is not a physical system but a software that has spread globally through connected devices. In a desperate move to prevent the launch of Genisys, the Terminator sacrifices himself by entering the core and initiating a time displacement explosion.
The explosion destroys the facility and seemingly prevents Genisys from launching. However, a post-credits scene hints at a possible sequel, suggesting that the war against Skynet is not entirely over.
In summary, “Terminator Genisys” ends with the destruction of the Genisys system, the sacrifice of the Terminator, and a hint at potential future conflicts with Skynet. The film utilizes time travel elements to create an alternate timeline within the Terminator universe.