He was best known for playing the killer Cole in The Sting, hockey goon Mo Wanchuk in Slap Shot, mobster George in The Untouchables (1987) and the gruff Henry Wingo in The Prince of Tides (1991).
Theater critic Clive Barnes in The New York Times called the two "quite jolly" and that they "deserve to be congratulated on the lack of embarrassment they show when, on occasion, they have to wander around stark naked.
[9][10] Sullivan was then featured prominently in director George Roy Hill's hit The Sting (1973), playing Cole, the hired killer who dogs the Robert Redford and Paul Newman characters.
The following year, Sullivan earned a Drama Desk Award nomination for Outstanding Featured Actor in a Musical[11] for his performance as steelworker Mike LeFevre in Working (May–June 1978), adapted from the book by Studs Terkel and also starring Patti LuPone and Joe Mantegna.
[12] Sullivan's other feature film credits include Walk Proud (1979), The Island (1980); Ghost Story (1981); Tin Men (1987); The Untouchables (1987); Funny Farm (1988); Dead Bang (1989); The Dream Team (1989); The Abyss (1989); Guilty by Suspicion (1991); True Colors (1991), The Prince of Tides (1991); Sister Act 2: Back in the Habit (1993); The Fantasticks (made 1995, released 2000); The Jerky Boys: The Movie (1995); Canadian Bacon (1995); and Bushwhacked (1995).
He had recurring roles on I'll Fly Away, as Mr. Zollicofer Weed, the ex-Marine turned wrestling coach, and NYPD Blue, as Patsy Ferrara, a retired prizefighter who taught Bobby Simone about keeping birds.