Some affronts are so heinous that typical recourse doesn't suffice -- a cheating lover requires more than wardrobe on the lawn, and an unjust demotion won't be eased even by hundreds of fancy swindled pens. Serve the justice of your dreams*, with Revenge Crabs.
Hiding their identities to avoid legal punishment, RC's clandestine operators aid bandit retribution by shipping packages filled with "tiny, purple dots"...or, technically speaking, horrible horrible pubic lice dots. To exact revenge you can sprinkle your little buddies on bedsheets or towels, dump em on a car seat/desk chair, or even infest yourself in order to deliver the goods face-to-face -- or face-to-back, if you groovy kids are feeling it. Doubt-assuaging testimonials range from the likes of Haley Y. of Chicago, who doused her boyfriend and watched a backstabbing coworker flare up shortly thereafter, and crabcipient Tyler D. of Toronto, who said that he'd be upset if it wasn't such "crazy payback" (crazy? crazy like a crab, maybe.).
If you're too gruntled to stoop to this level, RC notes that some folks actually drop a few on themselves to "seem more popular sexually". This also presents a conundrum: what vengeance will your one-night stand take after catching the itch due to your preemptive auto-crabbing?
*sadly, the dream is a nightmare, as this service is fake