What If ... All Series Had Season 6 Character Deaths?

In the last episode of season six of "Star Trek: Deep Space Nine," audiences were in for the shock of their lives - Lt. Cmdr. Jadzia Dax was killed by a possessed Gul Dukat. No one saw it coming, and many fans were left bereft that one of their favorite main characters had been taken away. Whatever the behind the scenes story was of contracts and labor-management negotiations, this meant the final season of the series would be missing one its main stays - and introduced a replacement "Dax" with the character of Ezri.

The trio asks ... what if this happened in every Trek series?

They look at The Original Series, The Next Generation, Voyager, and Enterprise, determining which "main" character would shuffle off the mortal coil in the finale of a series' penultimate season and how it would be handled with a replacement (or not).