The character is a reference to Dostoyevsky's The Brothers Karamazov, a book set in 19th century Russia which as the title suggests concerns a family called Karamazov and deals with a lot of questions of religion and free will. A famous part of it consists of a story within the story called the Grand Inquisitor where a member of the Spanish Inquisition, encountering Jesus returned to Earth, arrests him and argues that humanity prefers the bread and miracles offered by the Church over the freedom Christ himself offered. The idea of a literal Inquisitor arresting the very man they ostensibly serve is very on the nose for the character Fyodor Karamazov from 40k! Also it's a perfect mirror of 40k, if the Emperor got up off the throne the Inquisition (or at least the part of it represented by people like Karamazov) would be the first to declare him a heretic.

Also the father of the Karamazov family is also called Fyodor Karamazov and he's just a wanton and callous bastard much like the 40k character. A real OG 'this person is just the absolute worst'. He's just a multidisciplinary piece of crap.