Yagoda misses (Kirov), Beria hits (Katyn, Manhattan Project, list goes on).
Simple enough analogy by my reckoning.
And Yezhov gets himself and everyone else killed when his munitions stores explode.
Indeed, I think Wolfpaw's point earlier about Stalin hardly being the only person who stood to profit by the elimination of a rising star in the Communist Party (namely anyone else who had ambitions for the top spot that wasn't named Kirov) is a pretty effective way to demolish the argument that Stalin was just unquestionably behind the Kirov assassination. Really it relies upon a rather fallacious notion that Stalin was the only member of the Communist Party who wasn't completely willing to rub out a troublesome opponent for the sake of political advancement, none of these were particularly nice people, least of all the inner circle and intelligentsia.
And that Stalin even needed to assassinate his rials. If Stalin really wanted Kirov gone then a confession could easily have been obtained. Assassinations are chaotic and breed confusion and suspicion, but an orderly arrest, trial, and execution would be controlled every step of the way by Stalin.