Worst negotiater ever
Spoiler alert:
In the beginning Willis wrote "Nobody dies today" on a sign even though the insane husband was about to kill his wife and child. Willis could clearly hear that the husband was insane. He was shouting into the phone and he did not listening to reason. So the obvious choice would be to shoot him. No real negotiator would make that big a mistake. Then the wife and child would live.
And then later he has the 3 kidnappers walking into a helicopter with the girl. But he stops them!!! And by some faulty logic they walk into the house again even though the helicopter was their way out. If they had continued into the helicopter the snipers could shoot Mars and make the other 2 guys surrender. That way only Mars would be dead and the girl and 2 of the kidnappers would live. And the kids life would never even be in danger. The house would not burn down and all the FBI agents and bad guys would not die. Furthermore Willis family would be set free as he had the DVD AND the money. Even in the worst case scenario, Willis family would go free and the kid and probably the 2 kidnappers would live! And remember one of the kidnappers was a good guy, he died for no reason.
Why the hell would Willis want to risk his life and the life of all those people?