an example that refutes or disproves a proposition or theory
an example or fact that is inconsistent with a hypothesis and may be used in argument against it.
Examples:
1. But for every example of democracy fading out or finding itself under attack, there are counterexamples of democracy and democratic activists moving forward and finding solutions.
2. Google's Pixelbook and the family of Chromebook devices from traditional PC makers give a great counterexample to the overbearing Windows experience.