Buford "Biff" Howard Tannen is the main antagonist of the Back to the Future trilogy. His 1955 self serves as the main antagonist in Back to the Future and the central antagonist in Back to the Future Part II, while his 1985A self serves as the main antagonist and his 2015 self serves as the overarching antagonist. He is a minor character in Back to the Future Part III.
Biff is the George McFly's bully both in high school and adulthood (in the original timeline), is in love with Lorraine "Baines" Mcfly, and also is the arch-enemy of Marty McFly.
Biography
Original TImeline
Biff had started bullying George Mcfly when they were young, constantly forcing him to do his homework for him. Since George lacked courage and self-confidence, he never knew how to stand up to Biff, who wasn't very smart and would rather have fun with his friends than study. His bullying continued even 30 years later, since they both worked in the same company.
Biff had been promoted because George had done all the paperwork for him, and kept taking advantage of George.
His love for Lorraine didn't fade either, even though she was married to George.
Back to the Future - Part I
One day, Biff and George have an argument, because Biff had crashed George's car, claiming that he had a blind spot while driving drunk. He forces George to pay for the damages with his insurance, and tells him how he will pay for the beer stain he spilled on his jacket. With this, Biff inadvertently ruins Marty's plans to go to the lake with Jennifer.
New Timeline
Marty, the youngest son of the Mcflys, accidentally travels to 1955 with the time machine of his friend, Dr. Emmett Brown. There, Marty, who interfered in their parents first encounter, manages to give a younger George some confidence, even standing up to Biff when he makes an inappropriate advance on Lorraine at school.
After Marty indirectly causes Biff to crash his car into a manure truck during a chase, Biff vows to get rid of Marty. Days later, at the school dance, Biff finds Marty ,who goes by the nickname "Calvin Klein", and Lorraine in Doc Brown's car, orders his gang to lock Marty in the trunk of a car ,which turns out to be being from the dance band, and attempts to sexually harass Lorraine.
George later shows up as part of an impromptu plan he and Marty made where George would see him with Lorraine, but seeing Biff inside, he realized the ransom was now real. Building up his confidence, George confronts Biff and tries to stop him from abusing Lorraine. Biff responds by trying to break George's arm, violently pushing Lorraine to the ground when she tried to defend him. This aroused the anger of George, who finally fights back and ends up knocking out Biff with a punch to the face. In this moment, Lorraine fell in love with George and they both went to the dance together.
As a result of the punched, George became more confident and Biff no longer had anyone to mess with, and since he no longer had anyone to do his job for him, he had to do things on his own. He eventually started his own auto detailing business, which he ran himself, and which by 1985 gained notoriety. The Mcflys were among his most loyal customers. At this point, Biff seemed to have changed, being subservient and kind to George and the Mcflys, but still trying to get away with as little work as possible. He also seems genuinely proud of George for publishing his first novel, ,since in the new timeline he works as a writer.
Personality
Biff Tannen is an abusive, obnoxious, arrogant, lazy, pretentious and impatient bully who always bullies people to get what he wants. Like the rest of the Tannen family, he has bullied the McFlys ,mainly George, from the start. During high school, Biff constantly forced George to do his homework, due to Biff being too lazy and/or dumb to do it himself, and would always make fun of George, telling him "Hello, hello, anybody home?" while hitting his victim on the head.
Biff also turns out to be dumb and unintelligent in his youth, not only forcing George to do his job for him, but also using his mixed metaphors incorrectly, saying "make like a tree and get out of here" instead of " make like a tree and leave". He was feared by most of the students at the school and less brave without his gang, ,Match, Skinhead and 3-D, and the only person he feared was Dr. Strickland. He has had a crush on Lorraine Baines since high school, but she never returned the feelings. He continued to take an interest in her for the next 30 years, even after Lorraine had married George.
However, after Marty travels back to 1955 and gives George some confidence, George is able to confront Biff on the day of the prom, stopping him from harassing Lorraine. George ends up knocking Biff down with a punch, winning Lorraine's heart in the process. This hit possibly ended Biff's bully days, as he now couldn't mess with anyone. In the modified timeline, Biff treats George and Marty with respect and even addresses the former as "Mr. Mcfly", he also seemed genuinely happy when George published his novel, implying that he was at least proud of his former victim.