Today's phrase can be used in many different situations.
You can say this when you feel sorry for someone or something.
A. Last night Roger's new laptop was stolen.
B. Oh no! Poor Roger !
A. Mari did not improve her TOEIC score, so she can not become a manager.
B. Poor Mari ! I know she studied so hard for that.
A. It was so cold last night the cat's ears froze off.
B. Poor cat !