I've just been doing some google searches in answer to this thread. I was wondering, too.
This certainly looks like the worst tsunami ever, measured in terms of human lives lost. There have been bigger ones in terms of the height of the waves, but they were much more local (a local tsunami in a remote bit of Alaska left marks on the mountains showing that it was something like 1700 feet high
... but I don't think it killed anyone, or maybe one or two people). All the same, there are a couple of previous tsumanis that killed many, many people - one in Japan killed nearly 30,000, and I think that most of the 36,000 people killed by the Krakatoa volcano eruption were actually killed by a 150-foot tsunami.
There have been even worse natural disasters - floods and earthquakes in Asia that have killed numbers of people approaching a million.
A supervolcano eruption in prehistoric times may have been responsible for almost causing the extinction of humanity, which is one reason why we have so little genetic variation these days ... our species may have gone through a "genetic bottleneck" after the equivalent of a nuclear winter which killed almost everyone 75,000 years ago. If there is ever another supervolcano eruption (there's one overdue in the US where the Yellowstone supervolcano erupts every 600,000 years or so) don't count on your chances of surviving, wherever you live in the world.
So it goes. Isn't mother nature wonderful?
*shaking head at all of this*