Lure the robot to the target in the center then go into any of the 4 squares marked "trap door". You will shoot out of a cannon and if the robot is still over the target you will land on it's head. He will try to squash you and a quick-time sequence will start. All you have to do is repeatedly mash the 1 random button that shows up and and you will dodge the attack and it will damage itself. Repeat 5 times and you win.
You can ignore the lackeys on the ground unless you need/want health, energy, money or experience.