10 Movies Where The Villains BOTCHED An Easy Win
3. Biff Tannen - Back To The Future
Granted, Marty McFly's (Michael J. Fox) real enemy in Back to the Future is time itself, as he struggles to untangle his temporal meddling and ensure that his mother Lorraine (Lea Thompson) and father George (Crispin Glover) fall in love and later conceive him.
Marty conspires to make an inappropriate advance on Lorraine at the school dance, giving George the opportunity to "rescue" her, but a spanner is thrown in the works when bully Biff Tannen (Thomas F. Wilson) intervenes, has Marty incapacitated, and forces himself on Lorraine.
George of course hadn't counted on having to actually fight Biff, and so Biff easily subdues him with an arm hold.
His only mistake? Spending about 20 seconds laughing and gloating with his back turned from George, giving George precious time to gather himself, clench his fist, and knock Biff out.
Had Biff just finished the job and knocked George out, George would've never had his big heroic moment and likely never gotten Lorraine to fall for him, in turn undoing Marty's existence.