A character in Kalevala. His story can be found from poems 31-36.
Kullervo is son of Kalervo. Kalervo got in trouble with his brother Untamo, who then proceeded to kill Kalervo and his family. Kullervo's mother survives - and Untamo's men take her with them as a slave.
Kullervo, after he was born, was not a nice person. He broke his bed. As he grew a bit, untamo noticed Kullervo was a potential threat, and tried to sink him in a barrel - but Kullervo survived (just got up and surfed). They tried to burn and hang him, but that didn't seem to help either. (Strong kid, huh?)
As Kullervo keeps growing, he is sent to do various jobs as a slave. First, he's told to cut down some forest. Well, he did that all right - and cursed the place so that nothing can grow there anymore. He was told to build a fence. Well, he did that too, a big fence no one can get over of, not even birds - and it had no doors, either. (See? Finns are good at building systems that have no Gates. =) He also mismanaged a problem with grain pretty well.
Seeing Kullervo was more of a trouble than a good slave, he sold him to Ilmarinen the smith.
Kullervo was then sent to herd cows. Ilmarinen's wife wasn't too nice to him - she gave him a bread for lunch, but baked a stone in it. Kullervo tries to cut the bread with his knife, the last object he had that belonged to his parents, but the blade breaks on the stone.
So, his revenge is terrible: He lets wolves and bears eat the cows, turns the beasts into cows, and gets them home. When Ilmarinen's wife comes to milk the cows, they turn back into beasts - and eat the lady in a matter of moments (but not without allowing her to say good last words, for dramatic purposes).
Now, on a way to pay taxes, Kullervo notes a rather good-looking person of opposite gender on the side of the road and, uh, seduces her. Afterwards, this woman notices that Kullervo is, in fact, her brother, and drowns herself.
After this tragedy, Kullervo goes to war and kills Untamo and his family, and returns home, only to find the folks home dead. He talks to his sword... and then kills himself with it.
Influencing others: You may find the ultimate fate of Túrin Turambar, as told by J.R.R. Tolkien, quite similar.