The most recent one that screamed in my mind. Bunnies thought they were being smart by not telling or helping everyone else that there's a table with additional dates sample at the Detour.. and they eventually still ended up finishing the task LAST.
Not that I wanted the other teams to be helped by Bunnies.. but it's just an irony or some would even say karma.
I can understand your classification of this as karma; however, I disagree that they only thought they were being smart: in my opinion it was a smart move. The Bunnies had an up and down race, they were prepared to take any advantage they could get their hands on and that is fair enough. It was Leo and Jamal who asked them for help: The bunnies owed them nothing, they were in no way obliged to help them and so their decision not to is in my eyes valid. Furthermore Leo and Jamal had been notoriously deceitful up to that point, would you trust a promise or a deal from them? I digress...
Tim and Danny had a hard time with the Polka task in Poland, not just with the dance but with having to dress as a woman. This task became their intro task video snip reminding us all of their embarrassment weekly (it must be difficult to watch for them if they haven't yet come to terms with it :S) to me that's a pretty harsh example of poetic justice (I don't think I condone the humiliation - my opinion)
Nicole and Travis u-turn the Afghanimals (S23E8) for being dishonest/not playing the game by Nicole and Travis's moral paradigm (my least favourite use of the u-turn is as a punishment: see season 16 and both u-turns in the mentioned leg). In the next leg Leo doesn't allow Nicole to see his completed roadblock instrument, punishing her for trying to break her own moral paradigm. Poetic justice, comeuppance, revenge, what you will.
This one is not concrete but it's still interesting: elephants appear in the legs that eliminate blonde girls
see christie and jodie, liz and marie, and ally and ashley.
Notable exception: dustin and kandace (like i said, not concrete)