bonitahi
I am not surprised that you keep getting people replying whilst using the wrong criteria that you set out.
Check out your thread title, and compare it with your OP, I think you’ll soon see why.
As for the OP, how are you determining which is the largest natural disaster? The Cascadia Earthquake/tsunami of 1700 would qualify on any scale, and if such an event were repeated there would certainly be more fatalities than Haiti.
You could also take a look at the 1960 Valdiva earthquake, which also led to tsunamis, landslides and a volcanic eruption.
Again, if this took place today, the Haiti event would be overshadowed.
IF you want to broaden out your perspective, to include disease, then Haiti is very small, the import of various diseases from European settlers devastated many indiginous populations, and killed many millions.
Perhaps the best knwo fo these would be Spanish flu, in the US alone this is estimated to be over 500k, and of course if you take the whole of the Western Hemisphere then that number rises.
There have een several waves of flu throughout the 20thC in the Western Hemisphere - though to be honest these outbreaks also affected the rest of the world too.
It does depend upon where you decide is the Western Hemisphere, do we mean the Americas? - That is rather less than a hemispere, given what that word actually means.
Anyway, I’ll see your Lisbon Earthquake Jimm and raise you a Santorini
http://www.stonepages.com/news/archives/002034.html
I find it interesting that the date of the eruption is at some dispute because it would put the chronology of many ancient civilisations out, its an archeology vs science argument.