The narrator accuses someone who has become too greedy to the point that success is defined not by personal gain but by others' losses.
The beginning describes the early life of the climber and a warning of the danger that life brings. The climber does find personal success, but is not content and continues climbing to find contentment, stepping over and eventually devouring others, who are all competitors.
This becomes the deadly dagger because the climber ends up suddenly dead. The reason? He or she has been eaten by somebody who, like they, were trying to define their own success.