"your deserved reward or just due" for an action taken or statement you have made. It always conveys that to be of a negative nature. It should be hyphenated as neither word, of it's own definition, conveys close to the meaning of the combination of the two; therefore the linkage of the hyphen is needed.
(Joe; therefore, got his just due or his come-uppance for his continual bragging and then, his abysmal failure.
Commonly mispelled as comeuppins.