Dumbledore was killed ontop of the Astronomy Tower by Severus Snape. His death led to the muggleborns to hide and the eventual downfall of Hogwarts. Dumbledore's discovery of the Marvolo Ring and the fake Locket, as well as the latter portion of his days led to the eventual finding and destruction of Voldemort's horcruxes and thus Voldemort's death.

Some words of wisdom:
"It matters not what someone was born, but what they grow to be."
"It does not do to dwell on dreams and forget to live."
"It’s the unknown we fear when we look upon death and darkness, nothing more." 
"Of course it is happening inside your head, Harry, but why on earth should that mean that it is not real?” "
"It is a curious thing, but perhaps those who are best suited to power are those who have never sought it. Those who have leadership thrust upon them, and take up the mantle because they must, and to find to their own suprise that they wear it well."
"Dark times lie ahead of us and there will be a time when we must choose between what is easy and what is right."
"“That which Voldemort does not value, he takes no trouble to comprehend. Of house-elves and children’s tales, of love, loyalty, and innocence, Voldemort knows and understands nothing. Nothing. That they all have a power beyond his own, a power beyond the reach of any magic, is a truth he has never grasped.” "

To every Harry Potter fan I ever knew, saw this post, or even subscribed to my channel, I salute you. I hope you enjoy this skin.