In the last episode "The last Vow" of the third season of Moffat's TV show, Sherlock and Watson broke into Magnussen's mansion to steal the proofs about Mary's past. But it turns out that Magnussen has no secret safe where he keeps evidences to pressure people and Sherlock finally decides to suppress the threat by killing him.
But, why Sherlock did not accuse him of defamation? In real life, press has a lot of power, and even a weakly supported claim can hurt a lot. Suspicions of murders get more room in newspapers than their rehabilitation when it is found out that they were wrongly charged. But, we are talking about Sherlock. He has a strong enough reputation and does not really care about people's opinion, so he could stand a mediatic fight against Magnussen. Especially since noone would believe that the innocent-looking Mary was a former professional killer if the media tycoon has nothing to support his claim.
In my opinion, this was a poor way to conclude the season. In particular, it makes Magnussen looks a stronger opponent than Moriarty. Steven Moffat is a reputed scriptwriter. What am I missing here?