Power is an interesting concept in this novel as the main characters have very little power. The men of the ranch are completely beholden to the owners for both their work and their home. People like Crooks have even less power as a black man in that time period. This is what allows Curley's wife to threaten that 'I could get you strung up on a tree so easy.'
Their lack of power is what makes George and Lennie long for a place of their own where they would have to answer to no-one, where they can have 'a little house and a couple of acres'.
Curley is seen as someone who abuses his power as the owner's son, always ready for a fight 'his hands closed into fists'.
Lennie has physical power as he is described as like a bear and it is this power that gets him into trouble and eventually leads to the killing of Curley's wife.