Schopenhauer

"Nietzsche considered him one of his most important teachers, and Freud, astonishingly, thought him one of the half-dozen greatest individuals who had ever lived. One of the few professional philosophers to treat him as more than a crank was Wittgenstein, who perhaps saw in his work an anti-philosophy akin to his own."

https://www.lrb.co.uk/the-paper/v47/n22/terry-eagleton/pregnant-with-monsters