When in doubt, try this simple trick: If you can replace the word with “he”’ or “’she,” use who. If you can replace it with “him” or “her,” use whom. Who should be used to refer to the subject of a sentence. Whom should be used to refer to the object of a verb or preposition. When to Use Who In a sentence, who is used as a subject. Let’s look at a couple of examples: Who would like to go on vacation? Who made these awesome quesadillas? When to Use Whom Whom is used as the object of a verb or preposition. Consider these examples: To whom was the letter addressed? Whom do you believe? I do not know with whom I will go to the prom. The Difference Between Who and Whom How can you tell when your pronoun is the object of a verb or preposition? Try substituting “he” or “she” and “him” or “her.” If “he” or “she” fits, you should use who. If “him” or “her” fits, you should use whom. Keep in mind that you may have to temporarily rearrange the sentence a bit while you test it. Who/whom ate my sandwich? Try substituting “she” and “her”: She ate my sandwich. Her ate my sandwich. “She” works and “her” doesn’t. That means the word you want is who. incorrect - Whom ate my sandwich? correct - Who ate my sandwich?

It's exactly the same as the subject + relative prounouns "el que" ("el que ríe último, ríe mejor") and used in the same way. This isn't something you'd normally say in conversation unless you're quoting someone, as in your example, or repeating a catchphrase/frase hecha, as in my example.

First of all, it’s not correct grammar. It should be “Punish him who has committed the crime.” We say “him,” not “he,” since it is the direct object of the verb punish. It is correct to use “who” (not “whom”), since “who” is the subject of the verb “commit.” It’s not how we usually speak. In fact, it sounds like someone is trying to use King James Bible language, and is getting it wrong. Usually, we’d say “Punish the one (or “the person”) who committed the crime.”