They're both rather silly, but I suppose if I had to choose one, it would be Picard's given they went all in with that death. Emotional final moments, with a glimpse of him walking into the afterlife then dying. Then we get a scene with the rest of the characters gathering around and commiserating his loss and grieving his absence. And then the very next scene, Picard's back.
Indeed, a popular rumor is that when the series was originally planned as a one and done, the intent was that this was indeed Picard's one true permanent death, which they reversed when the decision was made to do more seasons. I can believe it.
Honorable mention to Data's death in the Picard S1 finale, who is revived just long enough to say he wants to die finally and permanently, and we get a big emotional scene to show just that. Then he comes back in the third season.