How many attacks are allowed per turn when playing Monopoly Go?

The question contains a misunderstanding of the game rules; there are no "attacks" in traditional Monopoly, including Monopoly Go versions. Monopoly is a real estate trading board game where players roll dice to move around the board, buying or trading properties, and developing them with houses and hotels. Players collect rent from their opponents, with the goal being to drive them into bankruptcy. There might be some confusion with another game or perhaps a house rule from an individual's personal version of Monopoly. But as far as official rules go, attacking is not part of the Monopoly gameplay.