Helmut Zemo is the main antagonist of Captain America: Civil War and a major anti-hero in The Falcon and the Winter Soldier.
In the comics, the Zemo family were of German nobility, all of which were barons. However, Heinrich Zemo was allied with the Nazi organization H.Y.D.R.A., as a brilliant scientist yet a power-hungry aristocrat and supervillain with a grudge against Captain America, who he fought in World War II. His legacy was carried on by his son, Helmut Zemo, who formed the team of villains the Masters of Evil.
In the MCU, Helmut Zemo was a Sokovian soldier who lost his family during Ultron's attack on his country. Blaming the Avengers for his loss, he thus sought to tear them apart by staging a terrorist attack on the signing of the Sokovia Accords, setting off a chain of events that led to the Avengers fighting eachother and splitting up.
Baron Zemo was created by Stan Lee and Jack Kirby.