These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Not-leaving: An act of trust and love, often deciphered by children.
Liesel finally reconciling with Ilsa Hermann.
Iron Woobie: A vast majority of the cast. World War II does that to people. Though a notable example is Death, who has the most miserable job on Earth and still cares about humans.
Among others, there's Michael Holtzapfel's suicide, Rudy giving the teddy to that pilot, Death's way of describing Rudy when the bombs fall, and way, way more.
She leaned down and looked at his lifeless face and Liesel kissed her best friend, Rudy Steiner, soft and true on his lips.
The Standover Man is somewhere between this and a Crowning Moment of Heartwarming. A Jewish man writing about his friendship with a German girl on painted-over pages of Mein Kampf? Yeah. That's sad.
The death of Hans and Rosa and how Death remembers them.
This Troper has read the book several times over and STILL sobs like a child every time the last bit comes up.
This little line near the very end of the book:
Papa was a man with silver eyes, not dead ones.
Liesel imagining Hans sitting up and playing the accordion when she lays it on his chest after he dies.