https://www.refinery29.com/en-us/2019/11/8829052/mr-robot-season-4-episode-7-elliot-dad
The big reveal? Elliot was sexually abused by his father Edward Alderson (also Christian Slater).
We come to this horrifying realization in one of the darkest ways possible. Vera spends all of “Proxy” trying to force either Elliot or Mr. Robot to explain the latter’s existence. Mr. Robot is willfully hostile towards the inquiry, and Elliot is painfully confused. The hacker cannot remember the exact moment Mr. Robot was created or why he needed him in the first place. Elliot assumes the correct origin story is the one he has always told himself — Mr. Robot was born to deal with the death of his father and the physical abuse of his mother — but this hazy explanation immediately seems flimsy amid the dramatic grandeur of “Proxy.”