Flintheart Glomgold is Scrooge's archenemy and the second richest duck in the world. Unlike Scrooge, he did not make his money honestly, instead cheating and even stealing to become rich. He has his own Money Bin in Africa, which is where they first met.
History
Glomgold when he was a teenager
Scrooge and Flintheart first met in Africa when they were teens.
Flintheart in DuckTales