In his telling Eyes on the Prize 2 interview, he admitted to the lifelong discontentment, but not necessarily regret, for his actions against the Black Panther Party.
As seen in Judas and the Black Messiah, Bill O’Neal would comment on life as a car thief turned Black Panther Party infiltrator (in only his late teens, too) when interviewed for the 1990 documentary Eyes on the Prize 2, which the film initially recreates with Lakeith Stanfield before using the real footage at the end.
Bill O’Neal actually continued to serve the FBI as an informant until 1973 (years after Fred Hampton’s murder), at which point he entered the witness protection program.
Apparently, O’Neal’s suicide on January 15, 1990, was not his first attempt as his uncle claimed he had survived walking into traffic the previous September.