Final answer:
The Treaty of Versailles was signed at the end of World War I on June 28th and included a 'War Guilt Clause' that held Germany responsible for starting the war. Germany was required to pay financial reparations and cede territory.
Step-by-step explanation:
The treaty that was signed at the end of World War I on June 28th and included a 'War Guilt Clause' was the Treaty of Versailles. This treaty imposed harsh penalties on Germany, including financial reparations and territorial concessions. Germany was forced to accept full responsibility for starting the war and pay a massive indemnity.