Finn
One of the main protagonists of the new trilogy, Finn was introduced in The Force Awakens as a Storm Trooper who defected from the First Order and helped Poe Dameron escape his imprisonment. From there, he ended up on the planet Jakku where me met Rey and Poe’s droid BB-8, and helped the two of them escape the planet and join the Resistance.
Later, Finn used Luke’s lightsaber to take on Kylo Ren, and while he fought admirably, he was defeated and nearly killed.
Similarly, during the assault on Crait in The Last Jedi, when the First Order was charging a laser canon to destroy the blast doors to the Resistance’s base, after the initial attack to disable it failed, Finn, determined to destroy the cannon, flew his ship directly into the canon, attempting to sacrifice himself to defeat the First Order, before being stopped at the last second by Rose.
A common theme among Finn is that throughout the first two films, he continuously put himself in situations he barely survived in order to protect his friends and the rest of the Resistance.
If Star Wars Episode IX is the conclusion of his story, then he may finally get his “hero’s death” and die because of a noble act he does in order to assist his friends, as has been teased over the previous films.
However, in my personal opinion, I feel that if Finn were to die, it should be to help establish another character as a more hated villain. More specifically, I think he should be killed by Kylo in front of Rey to help intensify her hatred for him and make Ren seemingly irredeemable.
Rey is clearly the one who Finn cares for the most in the Resistance and that is probably the same for Rey. I believe that Episode IX should be built to a climactic fight between Rey and Kylo in a battle between the last of the Jedi and the last of the Sith.
To do this right, Kylo Ren needs to be shown as a ruthless and power mad killer, and since he was shown to be sympathetic towards Rey in The Last Jedi, something needs to be done to show that his character is far past any opportunity for redemption, and to do this I think he should kill the person Rey cares for the most.
In my ideal version, it may be a rough ending for the character, but it is one that would help to create a more interesting story.