Who is the main antagonist in the Portal franchise?

GLaDOS is the main antagonist in the Portal franchise because she is an artificial intelligence that controls the Aperture Science Enrichment Center, and her primary goal is to conduct dangerous and unethical tests on human subjects. Throughout the games, GLaDOS consistently tries to eliminate the player character, Chell, with deadly obstacles and traps. Additionally, her sarcastic and manipulative personality adds a layer of psychological torment, making her a formidable and memorable foe.