Nash started out in WCW in the early '90s with a variety of whacky gimmicks including Steel, Oz and Vinnie Vegas.
In 1993, Nash joined the World Wrestling Federation and became Diesel, originally Shawn Michaels' bodyguard.
After defeating Razor Ramon (a.k.a. Scott Hall) for the Intercontinental Title and winning the WWF Tag Team Titles with Shawn Michaels, Diesel was given the WWF Title in a match where he used only one maneuver against the veteran Bob Backlund.
Remarkably, Diesel reigned as WWF Champion for nearly one year, even successfully defending the belt against HBK at WrestleMania XI—widely considered the worst WrestleMania of all time.
In '96, Nash returned to WCW and helped found the highly-popular New World Order stable.
At Starrcade 1998, Nash booked himself to finally end Bill Goldberg's highly-publicized undefeated streak, at the same time also winning the WCW World Heavyweight Title. Nash dropped the belt two weeks later to Hollywood Hogan in the "Fingerpoke of Doom" incident that many critics believe was largely responsible for WCW's downfall in 1999.
Of course, Nash reigned a second time in '99 after defeating DDP. This stint featured the confusing Hummer angle, a mystery that went unsolved for most of the following year.
At a Thunder taping on January 25, 2000, Nash awarded himself the title in the role of WCW Commissioner, after stripping the belt from Sid Vicious, who had won the belt the night before. Only hours later, at the same Thunder taping, Nash lost the belt back to Sid.
In May of 2000, Nash won the WCW Title again at a WCW Thunder taping after he beat Jeff Jarrett for the belt. Jarrett had himself been awarded the championship after WCW Champion Ric Flair collapsed at the prior Thunder taping. Nash then proceeded to hand the belt back to Flair on the following Nitro, only to have Flair lose the belt later in the show to Jarrett.
Nash's final championship reign came during August and September of 2000, as WCW was in its final death throes.