Who was the antagonist?
Arguably, the antagonist in "The Destructors" is the setting itself: post–World War II London.
Many of the children in London were evacuated during the bombings and went through a prolonged period of separation, fear, and confusion. The new leader of the gang, Trevor, whose upper-class name is rejected by the others as he becomes known only as T., represents the nihilism that came about because of the destruction of London and the deprivations that families suffered. Also, the loss of Trevor's prestigious name also signifies the loss of prestige suffered by Trevor's father, who "came down in the world."
After so many buildings and homes have been destroyed in London, and with T.'s father having been a former architect, it is possible that the new leader of the gang feels a certain resentment toward Old Misery. His house has suffered no injury, while all the houses around it have been destroyed. Added to this is the fact Old Misery, whose real name is Thomas, was also a builder and decorator at one time. In this house, there is evidence of Old Misery's talent—there is a marvelously designed winding staircase that has been created by using opposing forces rather than any support.
T. decides that the gang will destroy the house, proposing a creative method of destruction: they will dismantle everything piece by piece and leave the outer appearance of the house intact. T. tells his group to "be like worms." When they finish, the walls will still be intact, so nothing will be suspected, but the entire inside of the house will be destroyed. T. instructs the boys to smash all the china and glass and ornaments, tear up papers, cut up pillows, and rip sheets. Later T. burns Old Misery's money, and they smash the furniture.
"You hate him a lot?" Blackie asked.
"Of course, I don't hate him," T. said. "There'd be no fun if I hated him.... All this hate and love," he said, "it's soft, it's hooey. There's only things, Blackie...."
T. thinks about how the destruction will be in the papers the next day. When Old Misery arrives home sooner than they expect, the boys trick him and he enters the lavatory outside. Then someone locks him inside the lavatory so that the boys can complete their destruction. The next day, a truck driver goes to work after the bank holiday. When he gets in his truck, which he has parked by Old Misery's house, he does not realize that the boys have tied the struts of the house to his vehicle. When he pulls away, he pulls down the house.
"The Destructors," by Graham Greene, could have three antagonists, depending how you look at the story. At first, it seems that T is the antagonist. Blackie is presented as the true leader of the group, concerned about keeping the gang together. But T usurps Blackie's power with his plot to destroy the Thomas house. The struggle for leadership between T and Blackie serves as one of the major conflicts in the short story. Here we see the conflict between a more benevolent and somewhat harmless leader and a ruthless, more dangerous one.
Mr. Thomas could be considered to be the antagonist to the gang of boys. They must complete their mission to destroy his house before he comes back to stop them. When he arrives early, the boys must use their wits to detain him in the loo. T is a master of manipulation here.
But most likely the true antagonist is the setting itself. It is post-war England. The children have been stripped of their innocence, their childhood. They live in bleak, war-torn surroundings, where beautiful objects of the past have been destroyed. Their parents are non-entities in the story, and the children are left to their own devices. They mimic the actions of their predecessors, choosing to destroy rather than create. Greene shows us how closely related the two processes are. It takes just as much discipline, teamwork, creativity, intelligence, and energy to destroy as it does to create. Mankind is often faced with this choice and often chooses as the gang the does.
Even the lorry driver at the end of the story is not horrified by the destroyed house. He only laughs. He too is numb to and accepting of destruction.