He was created by Negative Mario, and is a helper to continue his legacy just in case. He is not actually his brother, rather his son. He told him in his mind to kill Mario. He first punched away AGK and Stanley Jones, as he came out of a Portal. Mario was shocked right away and used a Hammer. It did nothing. Doomguy shot a bullet, it also did nothing. He used a war scream to scare Mario. AGK became a giant thanks to the Mega Mushroom, and tried to crush him. It still failed, so he used a Bomb Keyboard. You guessed it! It still failed. He was defeated by Inferno Mario with a Hammer.
He hates AGK the most out of everyone he fights, perhaps because he lost to a kid. One day he went after him three times. They all failed. He learned some new tricks while at it though. He has the power to clone, and what he does is pretend one clone is the real one, and he uses the other clone to sneak up on people. It worked the first time used. He tried to kill him with a Portal, but AGK used a random computer to stop that. Burgdorf joined in, and rolled a giant Bowling Ball at him. However, he picked it up and tried to throw it at AGK, AGK defended with a Bomb Keyboard. It ended with Burgdorf throwing another that whammed him in the head. But it doesn't end there
He returned again of course with another power, "Negative Confusion". This power makes colors a little negative and changed. At times it will feel as if you are on drugs. Sometimes the colors are just all black or something. Invisible objects start to appear, you can see them but they aren't there. He then tried to do the clone trick again, but AGK knew this time and whammed him.