Sullivan joined the World Wide Wrestling Federation (WWWF) as a mid-card face from 1974 to 1977.
Sullivan formed The Varsity Club upon arrival in World Championship Wrestling (WCW) with Mike Rotunda and Rick Steiner. They immediately started feuding with Jimmy Garvin because Sullivan wanted Garvin's wife Precious for himself. This feud lasted a while with Sullivan kayfabe breaking Garvin's leg at one point. Steiner left the group and was replaced by "Dr. Death" Steve Williams and Dan Spivey. They feuded with Dusty Rhodes, The Road Warriors, Rick Steiner and Eddie Gilbert. Sullivan even attacked Gilbert's wife Missy Hyatt. By late 1989, the Varsity Club was gone, and Sullivan formed the Slaughterhouse with Cactus Jack and Buzz Sawyer to feud with Rotunda. Sullivan took time off in late 1990 and returned in early 1991 as the manager of One Man Gang, Black Blood, and the Angel of Death. They cut El Gigante's hair and had a brief feud. Sullivan also was the masked Great Wizard briefly to manage Oz. His contract with WCW expired in August 1991.
In early 1993, Sullivan and his valet Woman went to Extreme Championship Wrestling, where he teamed with The Tazmaniac. The two won the ECW Tag Team Championship and feuded with The Public Enemy. Sullivan also had a bloody feud with Abdullah the Butcher. Sullivan left ECW behind and headed back to World Championship Wrestling in spring of 1994.
Upon his return to WCW, he formed a tag team with his kayfabe brother Dave Sullivan, a dyslexic character who was being picked on by The Nasty Boys (Jerry Sags and Brian Knobs). He enlisted Cactus Jack's help and beat them for the WCW Tag Team Titles. Dave was injured and out of action for a while and Sullivan split with Cactus after losing the titles. Sullivan defeated Cactus in a Loser Leaves WCW match at Fall Brawl.
Dave soon came back and dressed like his idol, Hulk Hogan. This infuriated Kevin, who hated Hogan, and they started feuding. Kevin brought in Hogan's best friend, The Butcher, to help him with his feud against Hogan. He also brought in Avalanche and called the trio The Three Faces of Fear. They feuded with Hogan, Randy Savage and Sting. In early 1995, after not being able to end Hogan's career, Avalanche left the group and Sullivan turned on The Butcher.
Later in 1995, Sullivan began hearing the voice of someone calling for him to come find him. Over the course of several weeks, vignettes were shot with Sullivan searching for the man, who eventually became known as The Master. Once Sullivan found The Master, he was rechristened with a new gimmick, The Taskmaster. The two men immediately started putting together a new group that eventually became known as the Dungeon of Doom. In time, the group grew to include Kamala, The Barbarian, Meng, The Yeti, Hugh Morrus, Loch Ness, One Man Gang, Big Bubba Rogers, and The Giant. Sullivan also brought in his former Three Faces of Fear stablemates, with Avalanche wrestling as The Shark and The Butcher wrestling as The Zodiac. For a very short time, Big Van Vader also was a member. Managed by Sullivan, four Dungeon of Doom members lost to The Hulkamaniacs in a WarGames match at September's Fall Brawl. As a result of Hogan's win over Zodiac, he got to spend five minutes alone with Sullivan. The feud with Hogan continued for much of the remainder of the year and saw the group add Jimmy Hart as its manager, after he turned on Hogan in October 1995 and cost him the WCW World Heavyweight Championship in a match with The Giant.
The Dungeon then feuded with the Four Horsemen, and Sullivan acquired a certain disliking for Brian Pillman. Once Sullivan sent Pillman packing, the Dungeon and the Horsemen joined forces again to get rid of Hulk Hogan and his friends and formed the unsuccessful Alliance to End Hulkamania.
Afterwards, Sullivan and Horseman Chris Benoit began a feud much like Sullivan had with Pillman. This feud lasted for over a year however, with Benoit "stealing" Woman from Sullivan. Sullivan brought in Jacquelyn to help him and also added Konnan to the Dungeon. Sullivan lost a retirement match to Benoit at Bash at the Beach on July 13, 1997.
Sullivan made a brief on-screen appearance with the reformed Varsity Club of Mike Rotunda and Rick Steiner with their cheerleader, Leia Meow. After a couple of months, he was back off television. Sullivan was fired before WCW's sale in 2001.
Sullivan passed away on August 9, 2024.