The title of Baron Zemo has been passed from father to son for thirteen generations that span Marvel's history, though comic fans are most likely to know about the terrible exploits of the last two Barons, Heinrich and his son Helmut Zemo.
These two generations have been terrorizing the citizens and the heroes of the Marvel Universe for almost an entire century, and while Heinrich kicked off their reign of evil, Helmut has been doing his absolute worst to outdo his father and become the greatest Baron Zemo, though he was briefly sidetracked by his time with the heroic Thunderbolts.
10 CREATED SUPERHUMAN WMD'S
Baron Heinrich Zemo rose to power in WWII alongside other Nazi leaders like Red Skull and Baron Wolfgang von Strucker, and he used his brilliant scientific mind to create various doomsday weapons, including his own superhuman creations.
While he would more famously create the technology that gave Wonder Man and Atlas their ionic based powers, he also brutally reverse-engineered the original android Human Torch's abilities to create an army of Inhuman Torches, though they were defeated by a time-lost Thunderbolts team.
9 "KILLED" BUCKY AND FROZE CAPTAIN AMERICA
Heinrich Zemo made a lot of enemies during the war and into the modern Marvel era, but none were as lasting as his rivalry with Captain America, which extended beyond the decades and would ultimately consume the 12th Baron Zemo.
Captain America and Bucky's final battle in WWII was with Heinrich, who had captured and tortured the Allied heroes while he weaponized an experimental new drone. Cap and Bucky escaped to stop the drone, but it exploded and presumably cost Bucky his life and put Captain America on ice until the Avengers later found him.
8 CREATED THE MASTERS OF EVIL
Heinrich Zemo would live past the war and escape to South America, where he would enslave a small village to build his new secret laboratory where he hid for years, taught his son Helmut, and employed mercenaries like Erik Josten/Atlas.
When Captain America returned with the Avengers, Zemo was enraged and rededicated his efforts against his old enemy. He founded the Masters of Evil alongside Black Knight, The Melter, and Radioactive Man, though the team would go through quite a few different line-ups over the years after Helmut Zemo took over.
7 ATTACKED AVENGERS MANSION
Helmut allied with villains like Arnim Zola and Red Skull when he first took on the title of Baron Zemo, though he soon formed a new version of his father's team when he assembled the larger roster of Masters of Evil fans had ever seen.
This grouping of powerful villains laid siege to Avengers Mansion, injuring a number of Avengers, including longtime butler Jarvis and Hercules, who was beaten into a coma. The siege was ended after the final battle between Captain America and Zemo left the new Baron beaten after he fell off the roof of the mansion.
6 BRAINWASHED KIDS TO CREATE THE KINDER
Helmut recovered and married a woman known as the Baroness, who had creepily claimed to be a cloned version of his father Heinrich Zemo, and the two disappeared to his family's Castle Zemo, where they decided to start a family.
However, their family was made from kidnapped and abused children that they had brainwashed with their own idealism and an intense hatred of Captain America, though he was able to free them and capture the Zemos.
5 LEAKED THE THUNDERBOLTS IDENTITY
Baron Zemo tried a new tactic to gain the public's trust after the Avengers and Fantastic Four appeared to die during the Onslaught event, so he disguised his Masters of Evil as the heroic Thunderbolts, and himself as Citizen V.
However, when he saw the other T-Bolts were being corrupted by their new heroic identities, he leaked the truth about their criminal pasts and launched his plan to take over the world, though he was stopped by his former teammates and the Avengers.
4 TRIED TO STEAL THE WORLD'S SUPERPOWERS
Zemo and the Thunderbolts would find themselves trapped on Counter-Earth together, where they became heroes and essentially gained control of the dying world that lacked superpowered heroes before they returned to Earth.
Zemo was inspired by their ease of conquest there and created the Liberator device, which allowed him to absorb the various energies that powered heroes and villains across the globe. While he blindly thought he was saving the world, Moonstone managed to steal the energy, though she lost control and nearly destroyed the universe.
3 MESSED WITH HIS FAMILY TIMELINE
Helmut Zemo temporarily gained control of the powerful Moonstones used by his former ally, though when they were shattered he was sent on an uncontrolled trip through time that was linked to the blood of his ancestors.
He was able to witness the former Barons as he appeared randomly throughout time, where he found himself subtly intervening in the events, which included influencing his ancestor to kill his own father or by acting as the assassin himself, and while his actions weren't always fueled by evil, messing with the timeline is never good.
2 EXPOSED THE WINTER SOLDIER
When Bucky/Winter Soldier took over as the new Captain America after the apparent death of Steve Rogers following the first superhuman Civil War, Zemo set out to expose his father's former enemy by revealing his identity.
Zemo leaked Winter Soldier's past exploits as a brainwashed assassin and terrorist to the media to discredit the new Captain America, who he had also infected with personality-altering drugs. He further tormented Bucky by forcing him to relive the same event that led to his "death" and began his transformation into the Winter Soldier.
1 "KILLED" CAPTAIN AMERICA'S SON
After the Terrigin Mists were released into the atmosphere and triggered the global transformation of Inhumans, Baron Zemo and his Hydra organization attempted to use the toxic blood of a new Inhuman to sterilize the world, except the chosen few who were immunized.
Sam Wilson/Captain America and his partner Ian Rogers/Nomad intervened to try and stop their plans, though Cap and Nomad were separated. Nomad was defeated and Baron Zemo slit his throat before taking a picture to send to Captain America as a Christmas card, though Ian survived and helped stop Zemo.