malcontent

Dissatisfied with existing conditions.

A chronically dissatisfied person.

One who rebels against the established system.

Dissatisfied; discontented; especially, dissatisfied or discontented with the existing order of things, as with the constitution of society, or the administration of government.

A discontented person; specifically, a discontented subject of government; one who murmurs at the laws and administration, or who manifests his dissatisfaction by overt acts, as in sedition or insurrection.