Star Trek was never shy when it came to killing characters. It's just that the majority of them in the olden days were set apart by being either bad guys or red shirts. These days, the universe that has sprung out of Gene Roddenberry's Original Series is a lot more blood-thirsty and the first season of Picard proved to fit that model.
Over the course of 10 episodes, we got to meet a host of new characters, welcomed back old, familiar faces and watched as the universe, once more, tottered precariously on the edge of a mass extinction event. This wasn't a show so much just about seeking out new worlds (though one obviously formed a key part of it) but about preserving the old one.
In a pleasantly meta way, it was about reviving the past not merely to preserve it as a museum exhibit but to make it relevant. And whenever anything seeks new life, there is ALWAYS death involved. For Picard, those deaths were of new characters, old characters and bit-parts and they all mattered for different reasons. They just weren't all on equal footing, exactly.
But which ones were the most affecting, the most important to the plot and the best executed, if you'll pardon the pun?
This should go without saying, of course, but there will inevitably be HEAVY SPOILERS from this point on...