The complete subject: The longest, most boring day of his life; the complete predicate: ended with a dull thud.
There are two main types of both subjects and predicates - simple and complete. A simple subject/predicate includes one word only - only one noun/pronoun which is the doer of an action, or only one verb to denote that action.
On the other hand, the complete subject/predicate also includes all words tightly connected to the main word. In the example above, the simple subject would be the word day; however, the complete one includes all of the other phrases as well; the simple predicate would be ended; but the complete one has to include the prepositional phrase as well.