Human
A species that will destroy itself due to unchecked technological advancement. Humans have a level of intelligence sufficient enough for them to discover how to exploit environmental resources, leading to a subsequent increase in population. This increase in population requires more exploitation of environmental resources, leading to another population increase, resulting in a feedback loop of overpopulation and significantly altering the environment. As competition is naturally selected for its success in securing resources and reproduction, the human species is instinctually inclined to fight over resources, whether it be land, water, shelter, food, or mates. As humans discover how to extract more energy from resources, this fighting over resources, or war as we call it in modern times, gets more and more brutal as time goes on, going from arrows to guns to dynamite to atomic and thermonuclear warheads, to name a few examples. Overall, as humans become more advanced, they will not only lead to the suffering of their brethren, they will lead to the suffering of life all across the globe in their destruction of it.
"The human species is so overrated. They ruin the Earth, kill each other in increasingly violent ways, and continue marching toward the tens of billions in population despite all of this."