There are many examples of powerlessness.  The only one with power is the boss and perhaps Slim (to a certain degree). 

• Lennie is powerless in that he is slow mentally.  He cannot survive in the world without George.  He is completely dependent, even if he is strong as an ox.  Hence, he cannot take care of himself, which makes his powerless.
• George takes care of Lennie, which might suggest that he has power, but he is also powerless.  He is a migrant worker.  He is poor, does not have money, land, or status.  He goes where there is work and leaves when there is no more work.  He is expendable. 
• Curley's wife is another example of powerlessness.  She is powerless, as a women.  She is in a loveless marriage, and she feels trapped.  She has no agency to do anything. 
• Crooks is also powerless.  He is a black man who lives in a white world.  He has little interaction with the other men and is completely ostracized from everyone else.  
• Candy has been on the farm for a long time, but he is getting old.  He is feeling useless. At one point he even says that he wishes someone will shoot him when he gets too old. 
• Curley, even though his the boss's son, is powerless.  No one likes him, not even his wife.  When he acts up, the men say that they will beat him up.  Curley backs down. 

Based on these six examples, Steinbeck's world is filled with powerlessness.