How can Batman beat Superman so easily

Rating: Null/10 (4 November 2016)

Sorry if this has been brought up before but, Superman is not that stupid, ever if he fell for the first gas grenade, he surely would have seen the second one coming. Also it could have been over so fast if he wanted it too, it just bothers me that Batman could have killed him, only because Superman chose not to kill him in the first 10 seconds.. Wonder Women was actually Awesome IMO , loved her theme music, Not sure if the DC cut has been released or not but looking forward to it. I think this movie needed to be a Kevin Costner length film, lol.
IMO it needed more depth and I feel they portrayed the human race as gullible, way to easy they turned their backs on Superman.