Jack Welch, the CEO of General Electric from 1981 to 2001 died on Sunday. He was 84. The cause of death was renal failure, his wife Suzy Welch said. He led the company through 20 years of its greatest financial success and became the most influential businessman of his generation.

“Today is a sad day for the entire GE family,” current GE CEO, Larry Culp said in a statement. “Jack was larger than life and the heart of GE for half a century. He reshaped the face of our company and the business world. Jack was a strong and constant influence throughout my career despite never having worked directly for him.”

Welch was named “Manager of the Century” by Fortune in 1999. He was appointed Chief Executive a few months after Ronald Reagan took office as president. The business policies and lower tax rates greatly helped multinational corporations. In welch’s tenure. the value of the company’s shares on the stock market soared from $14 billion to more than $410 billion, an increase of more than 2,700%.

“He had a tremendous focus on shareholder value,” said Jeff Sonnenfeld, a Yale business professor and founder and president of the Chief Executive Leadership Institute, who taught Welch in the early 1980s.

Sonnenfeld noted that Welch also pushed GE into new lines of business, with mixed results. For instance, he presided over GE’s 1986 takeover of NBC-owner RCA. GE then sold the business to Comcast in 2013.

Under Welch, GE created one of the world’s largest banks, but GE Capital imploded in the 2008 financial crisis, nearly taking down the rest of GE with it.

“That provided a cookie jar. But it was a diversion that many European industrial giants didn’t get distracted with,” said Sonnenfeld.

Welch was also called “Neutron Jack” because he was quick to get rid of workers that he thought were not performing at a sufficient level.

President Donald Trump referred to this in a tweet about Welch on Monday morning. Along with sharing his sympathies for Welch’s family, he also called the Welch a “business legend,” “friend and supporter,” and said “we made wonderful deals together.”