There are countless examples of anticompetitive conduct going all the way back to prehistory. The legal vocabulary around it pretty extensive.

Since this is HN though maybe these will ring a bell :

* Intel's rebate program (https://www.ftc.gov/news-events/news/press-releases/2010/08/...) which ended up with a $1.2B payment to AMD

* Microsoft's notorious antitrust case (https://en.wikipedia.org/wiki/United_States_v._Microsoft_Cor....)

* AT&T abusing its monopoly status and being broken up (https://en.wikipedia.org/wiki/United_States_v._AT%26T)

Honestly this is such an obvious notion that the fact that you're asking for examples is suspect on its own.