This season, Butcher leveled the playing field against the supes by injecting himself with temporary compound V, an untested drug from Vought that gives the user powers for 24 hours. Butcher reasoned that it would help achieve their goal of eliminating Homelander once and for all.
And while V24 did give him laser eyes and super strength that allowed him to murder a supe named Gunpowder in seconds, his repeated use had consequences.
In addition to vomiting and bleeding from his ear, the use of V24 can lead to seizures, atrophy of the cortex, hyper-accelerated malignant tumors, and more side effects.
After fainting in the finale, a doctor told Butcher that attempting further treatment would significantly affect his way of life without necessarily extending the time he has left. Butcher was told that he had maybe 12 months left to live, 18 if they were being optimistic.
Butcher was also forced to confront his own childhood trauma this season. In episode seven, the supe named Mindstorm trapped Butcher in an endless nightmare.
In the nightmare, he relived his most painful memories that involved his father, Sam, physically and verbally abusing him and his younger brother Lenny. This constant torment combined with Butcher's abandonment led Lenny to take his own life.
The endless nightmare also showed that Butcher's own coldness and tendency to be violent stem from how his father raised him. In rewatching his past play out in front of him, Butcher realized that he was leading Hughie, who reminds him of Lenny, down a similar path of darkness.