If I had to summarise how to reveal the character of your protagonist in simple terms, it would be show how your character reacts to things that happen. Notice, it’s not just a reaction to things that happen to them, but generally. One of the darkest things that can happen around your protagonist is the death of someone close to them. This is why it is so revealing.
If death happens to your protagonist, their story is over (setting aside the obvious exceptions, eg The Lovely Bones). But if it happens to their child, their parent, their best friend, their whole family, their pet ferret… that is character development.
Imagine how revealing it would be if your protagonist lost her axolotl and failed to get out of bed for a month? Or her son was murdered but she keeps soldiering on with a smile plastered on her face? Maybe your protagonist’s mother falls down dead from an aneurism and she starts tap dancing with joy? This opens up rich possibilities for the relationships within family and community, not to mention how those around your protagonist act in turn.
Death is universally significant because we all face it. It evokes powerful emotional reactions from the reader. We can all relate to the gnawing anxiety that we will lose someone close and we won’t cope. Or the guilt that we will cope when maybe we shouldn’t.
Whether or not you include a death in your story, workshopping your protagonist’s reaction can open up possibilities and character development very quickly.