Of the top of my head, I'd say about half a dozen PCs have met their end in my 5e games.
Most memorable one was also from our most recent game. I'm running the original Slavelords series on-the-fly (straight up one-for-one conversion). The party is in Slave Pits of the Undercity, which has some dopplegangers in it and one of them infiltrated the party as a slave in need of rescue. Later, with the doppleganger still with them, the party decided to scout ahead while leaving one character alone to protect the "slave" (its a long story as to why this was decided). They even barricaded the exits so that no one could ambush them. With the rest of the party absent, the doppleganger saw his opportunity and attacked the PC, who failed on her Perception to see the attack coming. Combat ensued, and the PC put up a valiant fight, but she was eventually killed (even failing her first three death rolls in a row). The doppleganger dumped her body down a nearby dead-end tunnel, cooked up a cover story, and has now assumed the role of the dead player with the rest of the party - with the player taking control of the doppleganger to complete the ruse. Not sure how long it will take the group to figure it out, as the dead PC was a druid with many abilities the doppleganger can't pull off, but it will be interesting to see how this turns out.