Mr. Potter (Lionel Barrymore)’s Timeline and Summary

Mr. Potter is a rich, villainous guy who's trying to control the financial futures of Bedford Falls. He's on the board of the Building and Loan, and he tries to force George's dad to be less lenient toward the people to whom he lends money.
After Pa Bailey dies and George takes over, he fights with George over the same issues and becomes increasingly successful.
At one point, Potter offers George a job in order to shut down the Building and Loan—but George refuses.
Finally, Potter finds the $8,000 that Uncle Billy lost and steals it. When George begs him to bail him out, Mr. Potter berates him and then calls the police, asking them to arrest George for losing his customers' funds.
In the end, this plot fails, and we see nothing more of Mr. Potter after George wishes him a merry Christmas, and Potter says, "A merry Christmas to you—in jail!"