All Quiet on the Western Front is full of such events, and Paul, the narrator, frequently refers to the war in these ways.
Perhaps the one event that embodies all of these aspects of war is Paul's death, which occurs at the very end of the book. The reader learns in the book's final sentences that Paul died in October of 1918, just a few weeks before an armistice was agreed to end the fighting. His death, which is utterly pointless, underscores the fundamental absurdity of the war.
Another episode that demonstrates these themes is his encounter with the French soldier in a bomb crater in chapter nine. He is trapped with the man and stabs him, mortally wounding him. This episode demonstrates the savagery and godlessness of war. As the man dies, Paul is overcome with remorse, having killed a man with his hands for the first time.
Another event is Katczinsky's death, described in chapter eleven. Kat is wounded but not mortally, and Paul helps him to the field hospital, leaving him there. When Paul returns, he discovers that his friend is dead, having been hit, randomly, in the head by a piece of shrapnel. This demonstrates the uncertainty of war.
In chapter six, the men see stacks of coffins as they head to the front. The coffins, of course, are for them, and this also illustrates the uncertainty of war—any one of them could wind up dead.
Finally, the book is full of accounts of how the war is truly godless, how it has dehumanized the men. As Paul observes at the end of an especially brutal French offensive, the men "are forlorn like children, and experienced like old men . . . we are lost."