"Resentful" means bitterness at having being treated unfairly. It does not mean that you are only angry at higher-status individuals. You might feel resentful if you thought that one of your classmates or colleagues treated you unfairly or badly - it would not have to be someone of higher status. I can feel contempt for many politicians, even though they (in theory) have higher status. I held the bosses at the failed firm Enron in contempt for their dishonesty, even though they certainly had higher status than I did. [If you don't know what 'Enron' is (or was), do an internet search.]