Why does Doom hate the Thing?
In Fantastic Four #40, Doom invaded the Baxter Building, then headquarters to the Fantastic Four. Confident that he had prepared for all of the FF’s powers, he confronted Ben Grimm, the Thing. Grimm not only withstood Doom’s assaults (albeit with great difficulty), he actually dared to physically assault him, and wounded Doom. Doom has never faced a personal attack so severe, and he has sworn to destroy Grimm for that affront to his person.