What are some of the most disturbing paintings and artworks in history that you have ever seen?

Warning: Graphic Image (no longer shown) Below

When you say “"in history” I'm assuming you mean classical painters or artists of note. If that is your intent then this answer might miss the mark a bit. But when I read the “that you have ever seen” part of your question I immediately thought of the works of Joel Peter Witkin.

When I was just out of college I was working a second job at a book store. I was handling special orders one night (always interesting because often the SOs were books we would not normally put on the shelves). A customer had ordered the book “Gods of Earth and Heaven” by Witkin. It's a book of photography and his subjects were primarily people with physical deformities, staged cadavers, and body parts. Most everything was black and white. While the subjects were truly disturbing, many were beautifully presented and I was fascinated.

You can get a sense of his work by his own open call for models:

“Pinheads, dwarfs, giants, hunchbacks, pre-op transsexuals, bearded women, people with tails, horns, wings, reversed hands or feet, anyone born without arms, legs, eyes, breast, genitals, ears, nose, lips. All people with unusually large genitals. All manner of extreme visual perversion. Hermaphrodites and teratoids (alive and dead). Anyone bearing the wounds of Christ…women whose faces are covered with hair or large skin lesions willing to pose in evening gowns. People who live as comic-book heroes, boot, corset and bondage fetishists. Anyone claiming to be God. God.”

His most well known piece, “"The Kiss” was published in “Gods…” it depicts two, male severed heads placed to appear to be kissing. Upon closer view you realize it's actually one head that has been split down the vertical axis and the two halves are placed in opposition to each other.

(Edit: Apparently in some browsers The Kiss image popped up first as a preview despite my attempt to bury it within the body of the text as I had seen other posters do. I thought it simpler to just remove it altogether rather than inflict it on someone unsuspecting. You can Google it on your own should you so desire. You’re a smart cookie. But you have been warned.)

He's had other books. I saw one that was historic crime scene photos and images of women and children who had been committed to institutions. (If I recall correctly.)

Over time I became less fascinated with “Gods…” As I got older and more cynical it started to feel less artistic and more just damaged/desperate. I still own it, though. And the impact of the images is still strong.