Three kinds of massive, destructive forces mentioned in e.e. cummings's poem are a tornado, a blizzard, and a manmade apocalypse.
After the unheralded destruction of World War I, poets such as cummings viewed the world through a darkened lens. This poem of dread and destruction describes forces that cause mayhem and damage. In the first stanza the winds may blow "king to beggar," but the real secret to destruction will still be humanity.
Although all the forces of nature cause destruction, repairs can be effected. The tornado finally blows out and reconstruction can begin; a blizzard can freeze things and cause harm and damage, but it will pass.
It is humanity itself that is the most destructive, for its damage
...bites this universe in two,
peels forever out of his grave
and sprinkles nowhere with me and you(?)
Humanity is the only force that can cause such widespread and irreparable damage. Only humans can create the force that can do more than a blizzard or a tornado; only humans can break "this universe in two" with their hatred and wars.