The protagonist is the main character of a story, and the main playable character in the Manhunt games.
Traditionally, a protagonist is the main figure of a piece of literature or drama and has the main part or role. Alternatively, the phrase denotes a primary advocate of or proponent for a cause or movement. The main character can be a hero or a villain in a story regardless - it is just the character with the lead role. In literature, the protagonist may be characterized by their ability to change or evolve.
All protagonists of the Manhunt series share some similar qualities. All protagonists escaped or rescued by some in a locked and isolated place (Danny and Cash, respectively) or controls the main character (like Leo). Protagonists are always start at a place where they woke up then eventually betrayed by the antagonist.
The opposite of a protagonist is an antagonist, entities which are against the protagonist and their objectives. Much like how the protagonist's nature can be ambiguous, the antagonist could be either a hero or villain - they merely fight the protagonist.
Most antagonists in the game always show up as a voice, guiding the protagonist in their impending doom, until they are eventually killed.
So far, Leo and Danny are the only characters that were both protagonist and the antagonist in their respected "episodes".
Dr. Daniel "Danny" Lamb is the main protagonist of Manhunt 2. A former scientist of the Project, Daniel ends up in Dixmor Asylum, without any of his previous memories.
Leo Kasper is a major character and the deuteragonist, later revealed to be the true main antagonist of Manhunt 2. He is also the protagonist of the flashback missions.