12 Dumbest Decisions In MCU History
9. Ego Admitted To Killing Peter Quill's Mother - Guardians Of The Galaxy Volume 2
In order for Ego to complete his plan of absorbing every planet in the known universe, he needed the power of another Celestial. He spent millions and millions of years trying to find one of his offspring that actually carried the right gene, and finally succeeded with Peter Quill.
He managed to win his son over to his side with the light and the power within him, and even after explaining the details of the expansion to Peter, his only real objection was that his friends would die. Ego was able to kill these worries straight away by telling him that as Celestials, they were above such things.
Everything was going to plan, Peter was embracing his power, and planets all over the galaxy were being consumed, right up until Quill asked about his mother. Ego admitted to planting the terminal tumour in Meredith's head, at which point his son awoke from his trance.
All Peter asked was why Ego left his mother. His honest answer of knowing he couldn't return to Earth again because he knew he would never leave would have been enough. There was absolutely no need for him to tell Peter that he was responsible for Meredith's death. If he had omitted this detail, Quill wouldn't have turned on him, and there would have been no stopping him.