Tropical cyclone that struck East Pakistan in 1970
Source (Wikipedia): 1970 Bhola cyclone

The 1970 Bhola cyclone was a devastating tropical cyclone that struck East Pakistan and India’s West Bengal on 12 November 1970. It remains the deadliest tropical cyclone ever recorded and one of the world’s deadliest humanitarian disasters. At least 300,000 people died in the storm, possibly as many as 500,000, primarily as a result of the storm surge that flooded much of the low-lying islands of the Ganges Delta. Bhola was the sixth and strongest cyclonic storm of the 1970 North Indian Ocean cyclone season.