But although Lovecraft would probably appreciate his enduring popularity (considering he died poor and riddled with cancer), he would have hated the fact that it's because of goddamned Cthulhu. Before his death, Lovecraft admitted that Call Of Cthulhu wasn't his least-favorite story he ever wrote, but it was up there, being as he said, "rather middling ... full of cheap and cumbrous touches."
Like the part where fiction's greatest monster is defeated by a yacht that pokes him in the head.
No, Lovecraft's most-regretted story is the one that he happens to be second-most-famous for: Herbert West--Reanimator, which was adapted as Re-Animator, the most famous film based on his work, and the only one to date that really has anything to do with his source material.
Lovecraft wrote Reanimator on request from a friend, magazine editor George Houtain. At the time, Lovecraft was living in desperate poverty, and his buddy offered him a decent sum to pen a serialized story that could run for several issues and earn him a meaty paycheck. According to Lovecraft, he violated his artistic integrity to meet Houtain's requests to insert a cliffhanger at the end of each chapter, like some sort of early R.L. Stine and/or Dan Brown, and felt dirty about it for the rest of his life. It is unclear whether Lovecraft would have felt the same about his indefensible racism.