If I use brains to answer this question, probably shanks or luffy or both.
but any character death would be excruciatingly sad ... reason is because one piece doesn’t like deaths, we are not familiar with deaths in this series .... I think I once read there was a kid with some series disease that wished to meet Oda, he got his wish and Oda talked to him about OP ending, when the kid was asked what did he think of the ending ... he said: one piece is beautiful ... while crying ...
of course this is way in the past and Oda might have changed things.