Final answer:
Peter Grant was the manager responsible for Led Zeppelin's business negotiations throughout their entire career, improving pay and working conditions in the music industry.
Step-by-step explanation:
The manager of Led Zeppelin for their entire career was Peter Grant. His approach to managing the band involved heavy-handed business dealings, which included carrying a cricket bat for intimidation during negotiations with concert promoters. This assertive strategy led to significant improvements in pay and conditions not only for Led Zeppelin but also influenced the industry standard for many bands that followed. Grant's tactics were similar to the business acumen of Andrew Carnegie, who was known for his shrewd investments and consolidation in the steel industry. However, unlike Carnegie's contributions to the field of manufacturing, Peter Grant's legacy lies in the transformation of the music business and artist management during the 20th century.