I really like the fan fiction 'All Might: The Early Days'. It delves into All Might's backstory, exploring how he got his powers and the challenges he faced before becoming the symbol of peace. It gives a deeper understanding of his character.
One common theme is mentorship. All Might is Deku's mentor, so a lot of fanfics explore how he guides Deku, like teaching him how to use his power effectively.
Several characters have met their demise in the MHA manga, but it's a bit complex to list them all precisely. Some of the notable ones include [mention specific characters if known].