Isaac Kleiner is an evil doctor (or as we say in Sweden, and other civilized parts of the world: Professor) that lives on Earth in the Half-Life universe. He keeps a dangerous monster as his pet and loves to use other people as test subjects in his mad, capitalist-approved test and laborations.

It has been theroized that his power even surpasses the power of the G-Man.
Ondskan i dess renaste form

"DR. Onts" in it's purest form. This guy claims that he's Dr ont but his name is Kleiner. Fuck this guy.