@tanguatlay,
No comma, who.
https://grammar.yourdictionary.com/grammar-rules-and-tips/grammar-usage-who-versus-whom.html
The Subject/Object Connection
Next, it's also important to note "who" refers to a subject of a clause and "whom" refers to the object of a clause. So, if you think in terms of people doing something then "who," as the subject, is the person carrying out the action or doing something. Conversely, "whom," as the object, is the person receiving the action.
Example Sentences
Knowing "who" is the subject of a clause while "whom" is the object of a clause is one thing. Seeing it in action will help this stick in your memory bank.
Sentences Using Who
Let's look at a few examples with "who."
Who handed it to her?
His friend who lives in Austin came to visit.
I wasn't the one who made him feel unwelcome.
People who take time to be kind are rewarded for their good deeds.
Couples who hold hands stay together longer.
Remember, "who" is the person doing the action. As the subject of a clause, "who" tends to come before the verb of the sentence.
Sentences With Whom
Now, let's take a look at where "whom" lands in the grand scheme of things.
He is the one whom I love.
Why are we running and from whom are we running?
Those flowers came from whom?
He is our savior whom we adore.
Whom shall I call?
"Whom" tends to land after a preposition, like "from" and "to." It also tends to come after the verb of the sentence. However, that's not to discount it from being the first word in a sentence.
The important point to remember is that "whom" is receiving the action while "who" is performing the action. For example, "We will celebrate whom?" In this case, "whom" is receiving the action of celebrating.
The Best Way to Remember
If all that seems a tad too technical, here's the best way to remember when to use "who" and when to use "whom."
Use "who" when the subject of the sentence would normally require a subject pronoun like "he" or "she."
For example, "Who is the best in class?" If you rewrote that question as a statement, "he is the best in class" makes perfect sense.
Use "whom" when a sentence needs an object pronoun like "him" or "her." For example, "This is for whom?" Again, if you rewrote that question as a statement, "this is for him" sounds correct.