Since the details of 'the hitman real story' are unknown, the main character is the hitman for sure. He might have some sidekicks or partners in crime, though not all hitman stories have this. There could also be a love interest, perhaps a woman who is unaware of his true profession at first and then gets caught up in his dangerous world. And of course, there would be the people he is targeting, who could also be considered important characters in the story.
In a 'hitman real story', the main character is obviously the hitman. There could be other important characters too. For example, if there is a police detective who is on the hitman's trail, that detective could be a main character as well. And there may be some sort of mentor figure who taught the hitman his skills, if that's part of the story.
As I don't know the exact 'the hitman real story', I can't say for sure. But typically, there would be the hitman himself as the main character. There might also be his employer or the person who gives him the targets.