In terms of Hazel's character, they overhyped his motivation to what it actually was.
I was expecting some sort of betrayal/loss for the greater good. Something that deemed the "dying over and over again" punishment.
What we got was that his sister died during a training at Beacon. Kind of a letdown.
They then bring up whether she knew the risks or not. Hazel then says that she was "just a child." How old was she? Don't parents/guardians have a right to veto a child's admission as a Huntsman?
They made him illogical. If a family member dies in service to the military, do you blame the army he or she signed up for or the enemy that killed him or her? Why is he working for the person who controls the grimm that killed his sister? Bringing up my earlier point, wouldn't he blame his parents for allowing her to do it?