I can barely separate and prioritize plot/character when I write, as they are so closely intertwined in fiction. Nevertheless, I consider the prime purpose of writing fiction to be storytelling, so “plot” gets the nod, followed by character and then setting, also vitally important to fiction.
By definition, a piece of fiction (novel or short story) moves one or more characters through settings. Ideally, the character undergoes conflicts at various points in the plot until s/he must conform to the various pressures – i. e., change – and then move on through life. This process is essentially the same in a novel or short story, although by definition (again) a short story revolves around only one main character who learns one truth about life (at the climax), whereas a novel involves several major characters who may experience a number of “a-HA!” moments when learning various truths about life.
A character’s personality, therefore, depends up on what happens to him/her and how he reacts as the plot progresses, although a character can certainly influence the progression of the story.
Nevertheless, without plot a story is not a story; without character it is a description of setting; and in essence character and plot must combine to produce a story which takes place in a setting.
Complicated, yes – but so is life, and since Poe allegedly invented the short story, the process has worked, and the two fictional forms of novel and short story have entertained readers well.