From Wikipedia:
Mr. Linderman is a reputed mobster who has ties to several of the main characters. He is an avid chef and collector of art and antiquities, and is revealed to have the ability to heal living things in the Heroes graphic novel series “War Buddies” and the episode “.07%“. In person, he is persuasive, gentle and unfailingly polite. However, he has no qualms about extortion or assassination. He is even willing to allow the deaths of several million people in order to safeguard the human race.
In the graphic novel “War Buddies”, it is revealed that Linderman served with the Petrellis’ father in Vietnam, where the two were the only survivors of a mission to destroy a target called Au Co. Upon arriving at the target, Linderman healing a wounded Petrelli en-route, the pair discover an area of farmland with vast amounts of vegetation. They destroy the farm, which they surmise is being used to feed Viet Cong troops. They then realise that Au Co is actually the name of a young girl with the ability to make crops grow at an accelerated rate. Petrelli shoots Au Co, and prevents a horrified Linderman from healing her, a fact which at first leads Linderman to have utmost disdain for Petrelli. Years later, however, Linderman meets Petrelli again, and tells him that he now understands that sacrifices sometimes have to be made for the greater good.
In “Six Months Ago“, Nathan Petrelli and his brother Peter discuss their father’s connection to Linderman, and agree not to interfere with or expose that relationship, in spite of Nathan’s political aspirations. After an incident where Nathan is driven off the road by a mysterious truck, which he believes to have been sent by Linderman, Nathan and Peter decide to instead report their father’s relationship. When their father dies shortly before they are scheduled to testify against him, the brothers decide to end their mission to expose Linderman.