Mumbai's first major don was

Karim Lala was indeed one of Mumbai's first major underworld dons, part of the early triumvirate that included Haji Mastan and Varadraja Mudliar. He operated primarily in the 1960s-70s and was known for smuggling and other organized crime activities. Haji Mastan came later and became more famous, while Varadraja (Varadarajan) Mudliar was also an early don but not the first.