A redoubt is a fort or fort system usually consisting of an enclosed defensive emplacement outside a larger fort, usually relying on earthworks, though others are constructed of stone or brick.
Look up innuendo in Wiktionary, the free dictionary. An innuendo is an hint, insinuation or intimation about a person or thing, especially of a denigrating or a derogatory nature. It can also be a remark or question, typically disparaging (also called insinuation), that works obliquely by allusion.
Because (in the usage you linked to) it refers to the 'bad guy' from a film or book. In the more general sense, it means opponent or adversary. The OP is asking specifically for a term describing someone who takes pleasure in causing pain and antagonist does not carry that connotation.