scapegoat
A person unfairly blamed for problems they didn’t cause.
A scapegoat is someone who gets blamed for problems they didn't cause or aren't entirely responsible for.
Today, we use scapegoat to describe what happens when a group unfairly pins blame on one person to avoid taking responsibility themselves. When a team loses a championship game, they might make one player the scapegoat even though everyone contributed to the loss. In a family, one child might become the scapegoat who always gets blamed when anything goes wrong, even when siblings were equally involved.
Scapegoating often happens because blaming one person feels simpler than admitting a problem has many causes. It's easier for a class to blame the student who forgot the supplies than to admit they all procrastinated on the group project.
The word can work as a verb too: a manager might scapegoat an employee for a company's poor sales when the real issues were bad products and high prices.