You should have passed the exam.
Can be understood as:
You are very smart; the exam is very easy for you; but you didn't pass the exam.
You are very lazy; the exam wasn't that hard for you, but you failed.
How to correctly use should
in many contexts like this?
Update:
Answer to "Can you elaborate how you arrive at the second interpretation?"
google "define:should", the first result tells us:
used to emphasize to a listener how striking an event is or was. "you should have seen Marge's face"
emphasizing how surprising an event was. "I was in this shop when who should I see across the street but Tobias"