What I remember is the human and alien represent their respective species, unarmed, naked, and are separated by a force field. They cannot pass through this field but must kill one or the other to determine the winner of this galactic battle. The alien is round with protruding tentacles that end in pinchers. It grabs a lizard and plucks off a leg. The lizard is dead, and the alien tosses it toward the force field. The lizard passes through and lands on the ground next to the human. A moment later the human sees the lizard come back to life and scurries away...have to be unconscious to pass through the field. The human grabs a rock and runs toward the shield and hits himself in the head with the rock. He passes out but his forward momentum helps his unconscious body fall through the field and onto the alien's side. The human regains consciousness, kills the alien and the humans win the galactic battle.