Many species have caused widespread extinction on a level humans have barely approached. Cyanobacteria, for example: https://en.m.wikipedia.org/wiki/Great_Oxida

Many species have caused widespread extinction on a level humans have barely approached. Cyanobacteria, for example: https://en.m.wikipedia.org/wiki/Great_Oxidation_Event https://en.m.wikipedia.org/wiki/Great_Oxidation_Event.