At the moment the world's worst disaster is malaria and the mosquito that carries the virus. Although it really depends, as some people would judge i on deaths, others on property destruction
cyclones are the most worst natural disaster
The world's worst known nuclear disaster was at Chernobyl, in the Ukraine. The Chernobyl Disaster, as it is called, happened on April 26, 1986. There is a link to a Wikipedia article on this below.
It depends. The worst disaster can be anything. Like if someone you love dies or your house burns down. It's an opinion.
Gfth
what was the worst volcano disaster in the 20th century
An earthquake and the tsunami. It was the 5th worst earthquake in the world. The worst disaster for Japan.
The Cyclone Mahira in 1899 was the worst natural disaster in Australia.
Granville Train Disaster - 18 January 1977, Granville, New South Wales
eastland disaster
Since you have used the word "disaster" meaning widespread destruction and distress, I would have to say the terrorist attacks on 9/11 to the World Trade Center would be considered the worst aviation disaster that led to about 2,800 deaths. The worst aviation accident, would be the Tenerife disaster was the worst to 747's ran into each other 03/27/77 there were 583 fatalities.
Chernobyl, Ukraine, 1986
No such figure will ever be known. Certainly more than half the world will be aware of the disaster.