Jack Welch, the hard-charging former CEO of General Electric who bought NBC owner RCA in the 1980s, has died. He was 84.

Welch’s death was reported Monday by CNBC, where Welch made appearances after his retirement in 2001.

During his 20 years as chief executive, Welch turned GE into the one of the world’s largest and most valuable companies. The acquisition of RCA in 1986 for $6.2 billion put GE in the media business for the next 25 years. GE sold a controlling stake in what became NBCUniversal — after NBC bought Universal Studios in 2004 — to Comcast in January 2011. Comcast scooped up the remainder of the company in 2013.

Welch earned the nickname “Neutron Jack” for his relentless drive to cut costs, jobs and inefficiency in GE’s sprawling business operations, which ranged from high finance to large-scale engineering projects to consulting and brokerage firms. Welch was famous for his mandate that GE’s businesses be either No. 1 or No. 2 in their respective markets. ″Fix it, close it or sell it” was his motto, according to CNBC.

The GE takeover of NBC was rocky, as memorialized in jokes delivered on NBC’s “Late Night With David Letterman.” Letterman got a lot of traction out of a video clip of what he called “the GE handshake” after he arrived unannounced at the GE lobby in New York with a fruit basket and a video crew to get to know NBC’s new owners. An executive who met the late-night host in the lobby briefly extended his hand to Letterman, but then withdrew it quickly when he realized he was on camera.

A native of Massachusetts, Welch joined GE in 1960 as a chemical engineer. He was upped to VP in 1972 and was named chairman-CEO in 1981. On Welch’s watch, GE’s market cap soared from $12 billion to $410 billion. Welch helped set the template for the celebrity CEO. He was revered on Wall Street for his focus on results and willingness to make radical changes in pursuit of bigger profits. Under Welch, GE was known for its no-mercy approach to employee assessments and the need to weed out under-performers.

Welch tapped GE executive Bob Wright, who had cable TV experience during his brief tenure Cox Communications, to take the helm of NBC after the RCA transaction closed. Wright remained at the top of NBCUniversal until his retirement in 2007.

After retiring in 2001, Welch penned a memoir, “Jack: Straight From the Gut.” He and third wife Suzy Wetlaufer, former editor of Harvard Business Review, whom he married in 2004, were active as public speakers and in business education through the Jack Welch Management System online course.

Other books penned by Welch include “The Real Life MBA: Your No BS Guide to Winning the Game, Building a Team and Growing Your Career,” co-written with Suzy Welch, and 2005’s “Winning,” also with Welch. The company he left behind in 2001 has struggled under his successors. GE has sold off many assets that were considered core during Welch’s time. At present the stock is trading at about $11 with a market cap of about $96 billion.

“You’ve got to get truth in your company,” Welch told SiriusXM’s “Wharton Business Radio” program in 2015. “And you’ve got to get rid of the spin and all that. You’ll only get that if people trust you, if you’ve been authentic, if they know you have their back — all of these things. So, it’s so critical to get truth and trust because truth and trust provide a highly motivated team and winning team.”