Identify the complete adjective clause in He is one for whom message was intended?

Here's why:

* Adjective clauses modify nouns or pronouns. In this sentence, it modifies the pronoun "one".

* "for whom" is the relative pronoun that introduces the clause and acts as the object of the preposition "for".

* "the message was intended" is the rest of the clause, containing the verb "was intended" and its object "the message".

The entire clause answers the question "Which one?" and describes the specific "one" the message was meant for.