This was a story in a comic book. I don't know the title, nor the author or artist. It was definitely a comic book of (unrelated) horror stories, though. I believe I read it sometime between 1975 and 1980. (Unrelated stories – not a mainline title about a single character, like Swamp Thing.)
The story was about “the exterminator of exterminators” — a supremely confident and competent rat exterminator, who was sent into a basement to kill the rats there. The basement had a subbasement, and another subbasement … and the rats kept getting bigger and scarier .. until the rat exterminator met the rat exterminator, which killed him. The last line, of which I am very sure: “The rats he preyed on — brought in an exterminator of their own!”
Another story that may have been in the same book included one about a man who had been in a car accident, and wakes up in a hospital bed, paralyzed from the neck down .. supremely uncomfortable. His wife visits, and eventually tells him he's in hell, and will be in that uncomfortable hospital bed for all eternity…
A final story that may have been in the same book was about a sculptor, an evil man, who sculpted gargoyles and monsters that he had met in person, on his visits to hell. He died when one of his sculptures fell on him.