In 1986, Haku, in his rookie year in the World Wrestling Federation, became a star by bodyslamming Big John Studd on Championship Wrestling, though predictably, Studd's manager Bobby "The Brain" Heenan didn't pay him the $15,000 he promised to anyone who could do so. He made a name for himself in the WWF as half of The Islanders with Tama. Originally a fan-favorite team, The Islanders had mixed success, though they did win a $50,000 tag team battle royal at Madison Square Garden in October 1986. They turned heel in 1987 during a match on WWF Superstars of Wrestling with The Can-Am Connection (Tom Zenk and Rick Martel). Earlier in the show, heel manager Bobby Heenan had announced he would have a new tag team that night and everyone thought he was going to introduce a new team to the WWF. Instead he showed up at ringside during the match where it became known his "new" team was in fact The Islanders. The team had a classic feud with The British Bulldogs that was started when the Islanders, along with Bobby Heenan, kidnapped the Bulldogs' mascot, a bulldog named Matilda. Their feud ended after a six-man tag team match at WrestleMania IV, where The Islanders and Heenan (wearing an attack dog outfit) defeated the Bulldogs and Koko B. Ware, when Heenan pinned Koko.
In 1988, following King Harley Race's legitimate injury sustained in a match against Hulk Hogan, Haku was given Race's crown and robe and was rechristened King Haku. In one of his first big matches after becoming King Haku, he would face Hulk Hogan with Miss Elizabeth in Hogan's corner on Saturday Night's Main Event in October 1988. He would cement his position as king by successfully defending his crown against the returning Race in a match at the 1989 Royal Rumble. He would later lose the crown to Hacksaw Jim Duggan, who himself was crowned as "King Duggan". Haku would later go on to form the tag team known as The Colossal Connection with André the Giant and win the WWF Tag Team Championship from Demolition on 30 December edition of Superstars. Haku and André lost the titles at WrestleMania VI, when Demolition defeated the Colossal Connection to regain the titles. Haku never legally tagged Andre into the match (due to André's poor health). Late in the match André attempted to interfere, but Haku accidentally struck him with a savate kick which left André tied in the ropes; Haku was pinned shortly after this. The team's manager, Bobby Heenan, blamed André for the loss and even slapped the Giant, who retaliated by "paint-brushing" Heenan. Haku tried to ambush André; however, The Giant blocked Haku's kick and struck him repeatedly before leaving the ring alone to a standing ovation. André's face turn meant that the team had split.
Just after WrestleMania, Haku became the first wrestler to challenge the new WWF Champion, The Ultimate Warrior, but he lost the match. Later that month he was programmed into a house show program with Hercules. On a match that aired on the June 8, 1990 edition of the MSG Network, Hercules defeated Haku. In matches through April and May, the former Heenan family member won most of his matches against Haku. In the summer of 1990, Haku transitioned to an opening card wrestler on the house show circuit. He was victorious against the returning Brady Boone, Jim Brunzell, Barry O, and the newly arrived Shane Douglas. After being left off of SummerSlam 1990, Haku was first to be granted a series of matches against new Intercontinental Champion Kerry Von Erich in a series of house show matches in September. Winless in these matches, he then became part of the Heenan Family feud against The Big Boss Man and participated in the 1990 Survivor Series. Again winless, he moved on that fall to feud with the newly returned Davey Boy Smith. Haku ended the year mired in a lengthy losing streak.
In early 1991, he formed a tag team with fellow Heenan Family member The Barbarian. Their most notable match was a defeat in the opening match of WrestleMania VII against The Rockers (Shawn Michaels and Marty Jannetty). The team was short lived and Haku returned to singles competition, facing the newly returned Ricky Steamboat on house shows the spring of 1991. Shortly after competing in the Royal Rumble in 1992, Haku left the WWF.
In World Championship Wrestling (WCW), Haku wrestled as Meng in 1994. He was initially portrayed as the mysterious and intimidating bodyguard of Col. Rob Parker, wearing business suits and shades while maintaining a quiet demeanor. His last night as a bodyguard was at SuperBrawl V, when Hacksaw Jim Duggan wrestled Bunkhouse Buck; after the match, Meng attacked Duggan. Later in the event when Blacktop Bully was scheduled to wrestle Dustin Rhodes, WCW Commissioner Nick Bockwinkel came out and escorted Meng back to the dressing room because of the attack on Duggan earlier in the show. The next week, Col. Parker announced that Meng would no longer be a bodyguard, but a wrestler from now on, winning his first match against a jobber with one fast high kick. Teaming with Kurasawa, he feuded against Sting and Road Warrior Hawk.
Later, he faced Sting in a losing effort for the vacated United States Title at the 1995 Great American Bash. Meng later joined the Dungeon of Doom, forming a tag team named the Faces of Fear with his previous WWF tag team partner The Barbarian, with the pair being managed by another former WWF alumnus, Jimmy Hart.
Meng spent much of 1997 facing lower and mid-card performers before starting a small winning streak in the summer of 1998. This led to a main event WCW World Championship match with Bill Goldberg on the August 10 edition of Monday Nitro. Goldberg, too, had an impressive winning streak. Goldberg won and retained his title that night and thus added another wrestler in his winning streak, making it 160–0. Prior to this, Meng had faced Goldberg (before he won the World Championship) on WCW Saturday Night and, despite the loss, had pushed Goldberg for longer than anyone had until that point. In the spring of 1999, when Ric Flair was the president on WCW programming, the barbaric Meng would often annihilate Flair's enemies per his instructions. Later on, Meng had a short-lived feud with Sting and occasionally faced top stars like Lex Luger and WCW Champion Bret Hart. He also participated in matches for the newly introduced WCW Hardcore Championship toward the end of 1999. Meng finally won the title at the Sin pay-per-view on 14 January 2001. He became the final WCW Hardcore Champion.
Exactly one week after his WCW Hardcore Championship win at Sin, Meng returned to the WWF as Haku and made a surprise appearance at the 2001 Royal Rumble. After the Rumble, he formed a tag team with Rikishi, but the team did not last long due to Rikishi's injury. Haku was left to wrestle on the lower card shows like Sunday Night Heat. He was eventually released from the WWF, his final opponent being Shawn Stasiak on a WWF Jakked taping in Buffalo, New York on 23 July 2001. He would return to WWF house shows for a few months in the beginning of 2002.