When I saw Logan, there was something that made me rather curious about the film and that was the backstory on why Logan had taken Xavier away and had him hidden. All we knew from the film that there was an incident that happened on the east coast and that in Xavier’s confession recalling something that happened at Westchester before he killed by X-24.
My thoughts later about this got me thinking, could Xavier have accidently created Onslaught. There could be some truths to it since that we don’t know what before this film besides Mutants been born less and less. I think that there could have been some sort of fight that may have happened at the X-Mansion where Magneto (possibly brainwashed) lead an attack and he may have killed or injured somebody close to Xavier and then flipped out on him causing him to then start creating the Onslaught entity.
Then after this event happens strange things may have started happening to Xavier, maybe mood swings, losing his temper so forth and nobody picking up on what had happened until it was too late. Onslaught makes his play and starts taking out the X-Men and only being taken down by having Jean Grey or another strong psychic mutant to shut down Xavier’s mind and that a way to help supress this from happening again was Xavier was to medicate him.
This then leads to me where I think that is why Logan thought it was important to make sure that he was taking his medication as well as when his psychic powers got out of hand that he was medicated so that Onslaught wouldn’t manifest and cause more casualties like what happened in Westchester.
It’s just a crazy thought that I had and I don’t know if anyone else has the same thoughts about this.