Which survivor in Left 4 Dead sacrificed themself to save the other survivors?

In "Left 4 Dead," Bill sacrificed himself to save the other survivors because he believed it was his duty as the oldest member of the group. Despite his advanced age, Bill was a courageous and selfless character who knew his time was limited and wanted to ensure the younger survivors had a chance at survival. Choosing to stay behind and make a last stand against the infected, he gave the others a chance to escape and reach their destination safely. Bill's sacrifice was a testament to his sense of duty, bravery, and genuine care for his fellow survivors.