Biff Tannen

Biff Tannen is the main antagonist in the Back to the Future Trilogy, mainly 1 and 2. He was played by  Thomas F. Wilson.

1955
Biff Tannen, in the original timeline, started bullying George McFly when they were kids and never stopped. Over the next 30 years, Biff would continue to bully and intimidate George, as they both ended up working for the same company where Biff became George's supervisor (due to George doing all Biff's work for him to get promoted). Biff's crush on Lorraine never died either, although Lorraine had married George and presumably Biff had married as well.

1985 (Good Alternate)
However, things changed when the McFlys' youngest son Marty McFly accidentally traveled back through time to 1955 using his friend Doc Brown's DeLorean time machine, interfering with his parents' first meeting. Marty, using the anachronistic name "Calvin Klein," also manages to get on the wrong side of Biff by standing up to him, something which Biff was not used to. Marty was also indirectly responsible for causing Biff to crash his car into a manure truck, and this led to Biff finding Marty and Lorraine on the night of the school dance (November 12, 1955).

1985 (Bad Alternate)
Biff fades from existence. However upon returning to 2015 Biff became the victim of a time paradox: his giving the almanac to his younger self had changed the timeline, resulting in his nonexistence. He slumped behind a garbage bin fading into nothingness as the DeLorean flew away. The top part of Biff's cane remained in the DeLorean and Doc showed it to Marty as an indication that old Biff was there. As when Marty started to fade at the dance in the first movie, Biff did not fade out completely until the Delorean's distinctive sonic booms were heard. Presumably, had Marty and/or Doc found the evidence that Biff had been in the time machine, they could have corrected the time-line, but once they left 2015, Biff's fate was sealed.

2015
In the future Biff, age 78, in 2015, Marty, Doc and Marty's girlfriend Jennifer Parker traveled forward in time from 1985 to 2015 – unaware that their departure had been witnessed by Biff. Over the next 30 years, he remembered seeing the flying DeLorean taking off.