The grim, volatile foe of the protagonist, who, through a series of inexplicable events up to and including attempted murder, gains grudging respect for said hero (and may even save them) going from intolerable ass to tolerable ass. Frequently a Foil for the hero, who's ultimately a Mirror Character. Often they show what the hero could have become if fate was just a little bit different.
While they may be an antagonist in the broad sense of the term, the rival need not be an evil villain. The rival is one of the protagonist's more personal competitors. Their abilities and acheivements are routinely compared. They can motivate each other to improve, or frustrate each others progress.
If fate is unkind, they might ''turn'' evil. On the other hand, the rival might develop a genuine friendship with the hero and perform a Heel–Face Turn somewhere down the line. If they're ever forced to team up with the hero over a common threat, expect much awesomeness to ensue.
They may begin the series with a leg up on The Hero, which is often the catalyst for the hero's character development as their desire to best the rival inspires them to improve themselves. This may in turn inspire the rival to do the same once they finally meet someone who gives them a challenge — or worse, subjects them to an Embarrassing Rescue after surpassing them.
Even if they never perform a full Heel–Face Turn, they may develop into an Aloof Ally who is primarily concerned with being stronger than the hero, and since they see themselves as The Only One Allowed to Defeat You this means they will oppose other antagonists' attempts to kill the hero. Occasionally, a regular villain might go through a similar process and become a Friendly Enemy.
In the event that the rivalry is one sided they are the Unknown Rival. If a Rival thinks someone would perform better if they weren't focused on the opposition, they might deliver the "Run Your Own Race" Aesop.
Compare with the Arch-Enemy and Sitcom Arch-Nemesis, which may or may not overlap. The Lancer, is similar in personality but on the same side as The Hero, the rival may turn into The Lancer and vice versa through character development. Could be one of the Opposed Mentors. See also Fandom Rivalry. For a specific type of rival common to Shōnen Demographic series, see the Stock Shōnen Rival.
Contrast with Friendly Rivalry. For generation-gap rivals, see Intergenerational Rivalry.
