Restrained Revenge

This trope is when someone sates their need for revenge by taking a much pettier (or at least non-harmful) revenge on the subject before forgiving them. Typically in the form of a prank or superficial attack. The reasons for this can vary; the hero might have done something wrong (or attacked someone innocent by mistake, or taken down someone who deserved it) and actually been forgiven, or they might have been framed or made The Scapegoat, in which case it's likely to satisfy some sort of oath. Other times they may not have been planning a particularly serious revenge to begin with, but the audience or the victim assumes they are (for roughly the same effect) or it might be clear that the recipient deserves it (in which case its shows that they've already been forgiven).

If they swore to do something specific, they might invoke Exact Words to take a lighter revenge (for example, they might "take their life" by stealing their food, or humiliate them to destroy their social life).

Super-Trope to My Fist Forgives You (where the "revenge" in question is a physical blow) and the Paranoia Gambit (where the transgressor's own reaction to the threat of revenge is the revenge). Subtrope of Easily Forgiven. If this is used for an actual punishment rather than someone's personal grievance then it's an Unishment. Contrast Cycle of Revenge and Disproportionate Retribution (which it may also be used to Subverted Trope). If they don't want to admit it, they may claim it's a case of Villain's Dying Grace.

Examples of Restrained Revenge include:

Anime and Manga

In one episode of Trigun, Vash agrees to help a wealthy town mayor who is being threatened by a bandit leader...until he finds out the mayor murdered the bandit's peaceful family and took their land to build his town, at which point he stands aside when they confront each other. With the mayor's beautiful daughter pleading for her father's life, the bandit ends up shooting him in the leg instead of the killing he had originally planned on.
In Love Hina, Keitaro constantly gets Megaton Punched by the Tsundere cast (usually for something that wasn't really his fault.) There's at least two instances where the girl in question (Naru and Motoko respectively) realizes he was genuinely trying to help her, winds up for the usual violence, and then taps him on the head while he goes "huh?".
In Soul Eater, after defeating Chrona (who'd previously almost killed Soul), Maka delivers a mild version of the Maka Chop by lightly tapping him/her on the head with a book.
In an episode of Ghost in the Shell: Stand Alone Complex Bateau is tasked with tracking an old war buddy who's become a serial killer with the help of a couple of CIA agents ( Who are hoping he'll snap and kill him to cover up the war crimes he commited on their behalf). When he has him cornered he seems ready to kill him, but instead opts to empty his pistol into the wall and arrest him.

Literature

In the Tangerine, by Edward Bloor, the resident Badass protects his rep after being slighted by "kicking his ass"—literally, kicking him in the rear.

Live Action Television

In the Law and Order UK episode "Immune", after being asked to lie (pretending that Jake Thorne must have misunderstood him) in court, Casey gets even with Thorne by using his testimony to call him stupid (invoking Hanlon's Razor to explain why he was misunderstood).
In Scrubs after J.D. coaxes Elliot away from her fiance...only to realise that he doesn't want her. After spending the whole season being mad at him, Elliot gets her revenge by giving him a note that he assumes will tell his current Love Interest (and Elliot's mentor), Dr. Molly Clock, that she's forgiven him and she doesn't need to feel guilty about sleeping with him one mad dash later he gives it to Clock, who reads it and says it's addressed to J.D.; "Now we're even."
The Office: Michael initially threatens Dwight with losing his job after he finds out Dwight lied about his dentist appointment, and was actually meeting with Michael's superior Jan to try to convince her to give him the regional manager position. He forgives him after Dwight breaks down into pleas for mercy, and the two even watch a movie together, but he still punishes him by having him stand on a box the next day wearing a sign that says "Liar".

Web Comics

In DMFA, Jyrass is marked for Fey vengeance. Dan recounts his own experience, Creatures leave you alone, terrified of what the Fey in question will do to them if they interfere. The vengeance imposed upon Dan? All of his feathers fall out if he eats shellfish. What eventually happens to Jyrass? He's made Bachelor Of The Year. He hates the publicity.
Dangerously Chloe, Chloe used a golden opportunity to exact her revenge for being tortured earlier. She painted on the face of now-paralyzed Charity a theatric villain's twirled mustache.

Western Animation

Vinnie, a recurring character in Gargoyles, repeatedly suffers misfortune at the Gargoyles hands and finally seems to break under the pressure, muttering constantly that he's going to take his revenge. He has a huge custom gun made, which he names "Mr. Carter" and tracks down Goliath and threatens him with it. However, Mr. Carter fires... cream pies. After the pie in the face, Vinnie walks off humming, apparently satisfied with his revenge.
In Dan Vs. the Wolfman, Dan hunts down the eponymous wolfman responsible for scratching his car. When Dan finally finds him, his retribution consists entirely of keying the wolfman's car - and Dan is appalled that Chris would suggest he actually kill the wolfman for being a dangerous threat to society. For the sake of context, note that Dan once destroyed Canada because he slipped on some maple syrup. Disproportionate Retribution is practically the man's middle name.