Basic Trope: Characters are judged as good or evil based solely on their actions towards the protagonists, rather than their actions as a whole.
Straight: Hawkeye's best friend is Leo, a former bandit who's implied to have done some pretty questionable things in his past and isn't afraid to lie, cheat, steal and manipulate to get what he wants — but they're BFFs, so that's okay. Redd, meanwhile, is a charming, compassionate young guardsman working to protect their community... Unfortunately, he's also caught Suzy's interest, so Hawkeye, and the readers, hates his guts.
Exaggerated: Leo is an insane, murderous bastard who regularly makes a game of seeing how long he can keep his victims alive... but they're not anyone Hawkeye knows, so he's cool with it. Redd is Leo's polar opposite, an upstanding fellow in all regards — but since Suzy has a bit of a crush on him, he must die.
Downplayed: Leo has Loose Lips and often plays mean-spirited practical jokes on Hawkeye, while Redd often as not goes out of his way to cross Hawkeye's path in advance of him, just to neutralize traps that are in his way.
"He may be all heroic and super and such, which I respect, but that doesn't mean I have to like him."
Conversed: "I wonder why they write heroes who are so blinded by personal sentiment they ignore flaws in friends and virtues in rivals? It's not exactly endearing, really."
Leo decides to do Hawkeye a favor and Murder the Hypotenuse, attacking Redd. Redd successfully fights back and winds up slaying him; since Leo was such a horrible person, Redd is hailed as a hero while Hawkeye develops an even deeper grudge against him. Suzy grows tired of Hawkeye's Moral Myopia and leaves him; Hawkeye also blames this on Redd.
Alternately, Leo successfully kills Redd — and since Redd was so well-liked and he already had a record, he becomes a public enemy and the subject of an angry manhunt. Hawkeye attempts to protect him, but Suzy calls him out and "betrays" them, leading to Leo's arrest and execution.
Redd killing his best friend does give Hawkeye a perfectly valid reason to despise him. The fact that he killed Leo is also used as Foreshadowing that Redd has a dark side of his own.
Additionally, Leo was trying to help in a very warped way, showing that he indeed has a brighter side of his own.
Plotted A Good Waste: Telling the story from Hawkeye's point of view, the author intentionally used this to illustrate that Hawkeye's Fatal Flaw is his Moral Myopia; as the series progresses, the disconnect deliberately grows worse and worse and it becomes clear that Hawkeye is unknowingly setting himself up for a major fall.
Played For Laughs: Hawkeye realizes he should reevaluate his friend policy as he and Leo run from two federal agencies, the army, a coke dealer, and three assassin's guilds.
Played For Drama: Hawkeye's insistence on this leads him to alienate Suzy and destroy his public image as Leo's misdeeds grow in magnitude. Leo kills Suzy for leaving Hawkeye for Redd, forcing the rivals to team up to take him down. Redd does a Face-Heel Turn over the tragedy, vowing to destroy the society that allows the wicked to prosper at the righteous' expense.