The question is unfortunately too vaguely worded to be properly answered.
Did you mean “disasters that cause the most loss of life”? Because that might be the Bay of Bengal on a near annual basis. Because of its geography and the huge number of desperately poor people who live around its shore, on land that is barely over sea level, the annual – and expected – storms that run up the bay and bring heavy rains and storm surge with them, it’s not at all uncommon for tens of thousands of people to be killed there from year to year.
The lake you mentioned in your question has a huge potential for loss of human life – which hasn’t happened yet in recorded history – and some other African lakes have outgassed carbon dioxide in quantities that have killed thousands, but that’s a rare event, and frankly it’s rather minor on the scale of global events.
Earthquakes have always killed in the tens of thousands in areas that have not been properly prepared for them. (Last year’s earthquake and resulting tsunami off the coast of Japan killed thousands even in a place that is normally well prepared, but at least it wasn’t tens of thousands.) Earthquakes in rural areas of China, Iran, Turkey and of course, Haiti, have been extremely deadly and probably will be for centuries to come.
As others have mentioned, the USA experiences nearly all of the known “natural hazards”, from earthquakes, floods, mudslides, landslides and wildfires, to hurricanes, tornadoes, blizzards and droughts (minus the carbon dioxide and methane-filled lakes), but aside from notable disasters like Katrina, the loss of life is generally low, and the problems are more of convenience and cost to recover than they are about widespread loss of life.
And all of this, of course, is answered in human terms. To answer this question in terms of “other species” or “the environment” (minus humans), we would arrive at dramatically different answers.