Biography
Sometimes, even Laser-Guided Karma misses its target.
The character has done a number of things that deserve a karmic comeuppance, most importantly things that caused harm to the innocent. But when the time comes for the hammer to fall, that's not what happens. At least, not on them. They don’t get what they deserve. Instead, they get away scot-free. They are Easily Forgiven, maybe even praised, and even elected president. And they might even have reversed the Humiliation Conga that was being planned for them. Worst comes to worst, The Bad Guy Wins and a stolen happy ending takes place at the expense of the hapless victim who may be punished in the guilty character's place.
This is it. This is all there is to the story. The show is over. The book is finished. The author isn't going to write any more. The Word of God has been spoken. Karma is out to lunch. The villain has become a Karma Houdini.
Predictably, it is often shocking or downright upsetting to see such scoundrels dodge instant karmic punishment and come out triumphant in the end. But as frustrating as it is, it does not necessarily make the story "worse" as long as it doesn't feel forced, contrived, or even shortsighted. Regardless, this trope runs the high risk of leaving the audience's thirst for emotional catharsis unsatiated, especially when they've become so invested in seeing the villain they've projected their hate onto get their full commupance that may or may not come by the end. And when it doesn't, you can expect them to complain about it and clamor for a sequel where the villain does get their comeuppance — or alternatively, they'll try to satisfy their frustratingly unfulfilled desire for retribution by writing their own.
There can be a number of reasons for this trope. Sometimes, the story is going for a Downer Ending in which the villains escape justice for their crimes. Other times, the creators overlook relatively minor offenders, whether due to not considering their actions worthy of punishment or not having the time to see them get their comeuppance within the story. Still other times, it may not be possible to exact retribution on the characters who ends up becoming Karma Houdinis. It could be that they're too powerful to be subject to retribution — any Eldritch Abomination in a horror story is likely to be this, as even if they don't outright win, they are so beyond mortal comprehension that the best the protagonists can hope for is to simply escape them. Or it could be that there's no way to legally judge them because they are above the law in some way, and the protagonists are not willing to risk it all for some vigilante justice.
Compare Butt-Monkey, for which a character ends up having many disproportionately bad things happen to them throughout the story (and may also technically qualify for this trope, as hard as that sounds). The extreme counterpart of the former trope, Cosmic Plaything, can be considered this trope's polar opposite. Also compare with No Good Deed Goes Unpunished, where the good guy suffers as a result of doing the right thing.
Contrast the aforementioned Laser-Guided Karma, when the villain's comeuppance hits at an incredibly opportune moment and is directly traceable to their transgression; Karma Houdini Warranty, when the comeuppance only happens in a sequel; and Karmic Death, when the comeuppance leads to the villain's death. Also see Idiot Houdini, when a person is forever protected from the results of their stupidity.
Note that a character doesn't necessarily need to be a full-time villain to qualify for this trope. They may simply end up doing unnecessarily hurtful things, yet not suffer the repercussions. (In contrast, when someone is too evil to kill off, but may suffer other consequences, see Joker Immunity.)
Note also: The work usually must be completed for a character to qualify as this trope. Only if there are no more opportunities for Laser-Guided Karma to strike can a character be said to have successfully avoided any consequences for their actions. Exceptions may be made in cases where Status Quo Is God,note or when a character can be said to have permanently escaped, e.g. they died peacefully in their sleep at an old age. And sometimes even that’s not enough. (Unless they somehow managed to get into Heaven and are gleefully rubbing their current state in your face). Otherwise, resist the urge to put it on an ongoing work's page. If you are confident or know that the work has been cancelled before it can finish telling its story, it is valid as an entry.
Don't mistake a lack of direct karma for this trope. If a character, for example, murders someone and never gets caught, but a freak lightning strike kills them, they've still gotten their comeuppance even though the lightning had no connection to their crime. Think of the writer as God, with the power to punish or not punish a character who does evil.
Not to be confused with a literal Houdini-style escape by the villain to avoid justice, that's Villain: Exit, Stage Left, although the two certainly can (and often do) overlap.
This is a spoileriffic trope; spoilers shall be unmarked. You have been warned.