Confrontiamo il protagonista con l'antagonista.

It can mean either one.

Confrontiamo is the 1st person plural form of confrontare, so it can be:

• present indicative: we compare / we are comparing
• an exhortation: let's compare

Italian often uses the same form for both ideas. Context tells you which one is intended.
So this sentence could mean either:

• We compare the protagonist with the antagonist
• Let’s compare the protagonist with the antagonist

Because Italian usually drops subject pronouns when they are not needed.

The ending -iamo in confrontiamo already tells you the subject is noi (we), so Italian normally leaves noi out unless it needs emphasis or contrast.

For example:

• Confrontiamo il protagonista con l'antagonista. = We compare / Let’s compare...
• Noi confrontiamo il protagonista con l'antagonista. = adds emphasis, like we compare...

This is very common in Italian.

Because the article changes depending on the sound that follows.

• protagonista begins with p + r, so the normal masculine singular article is il
• antagonista begins with a vowel, so lo becomes l'

So:

• il protagonista
• l'antagonista

This l' is just the shortened form of the article before a vowel.

Because protagonista does not begin with one of the sound combinations that require lo.

Masculine singular nouns usually take:

• il before most consonants
• lo before s + consonant, z, gn, ps, pn, x, and sometimes y
• l' before vowels

Since protagonista starts with pr-, it takes il:

• il protagonista

Compare with:

• lo studente
• lo zaino
• lo psicologo

The apostrophe shows elision.

The full masculine article before a vowel would be lo, but in front of a vowel it shortens to l':

• lo antagonista → l'antagonista

Italian does this very often with articles before vowels:

• l'amico
• l'attore
• l'eroe

So the apostrophe is not optional here; it is the normal written form.

Italian uses articles more often than English, especially with nouns that refer to roles, categories, or known elements in a discussion.

So il protagonista and l'antagonista sound natural in Italian even where English might omit the in a more general statement.

In this sentence, the articles suggest:

• either specific characters already known in context
• or the two roles as identifiable concepts in a story being discussed

Leaving the articles out here would sound unnatural.

In this structure, yes: confrontare qualcosa con qualcosa means to compare something with something.

Here the pattern is:

• confrontiamo = we compare / let’s compare
• il protagonista = the thing/person being compared
• con l'antagonista = with the thing/person it is compared to

So:

• confrontare A con B = to compare A with B

This is a very common pattern in Italian.

Normally, no. For the meaning compare X with Y, the natural choice is con:

• Confrontiamo il protagonista con l'antagonista.

Using a here would not be standard for this meaning.

A learner should remember the pattern as:

• confrontare qualcosa con qualcosa

They have different functions:

• il protagonista is the direct object
• con l'antagonista is a prepositional phrase introduced by con

So the structure is:

• Confrontiamo = verb
• il protagonista = the person/thing being directly acted on in the comparison
• con l'antagonista = the second term of comparison

This is similar to English compare the protagonist with the antagonist.

Yes, Italian word order is somewhat flexible, but the basic order here is the most neutral and natural:

• Confrontiamo il protagonista con l'antagonista.

Other orders are possible for emphasis, for example:

• Il protagonista lo confrontiamo con l'antagonista.

But that sounds more marked or contrastive. For a learner, the original sentence is the best standard model to use.

Yes, in this case protagonista is a noun of common gender: the ending -ista can refer to either masculine or feminine depending on the person.

So you can have:

• il protagonista = a male protagonist
• la protagonista = a female protagonist

The same idea applies to many -ista nouns:

• il/la pianista
• il/la turista
• il/la giornalista

In your sentence, il shows that protagonista is masculine.

Yes. Antagonista is also a common-gender noun in -ista.

So you can have:

• l'antagonista = masculine or feminine singular before a vowel, depending on context
• if you want to make the gender clearer through the full article:
  • l'antagonista can refer to either a male or female antagonist in many contexts
  • plural forms would show gender more clearly:
    • gli antagonisti
    • le antagoniste

In your sentence, l'antagonista by itself does not clearly show gender, because the article before a vowel is the same written form for masculine and feminine singular.

It is pronounced roughly kon-fron-TYAH-mo.

The stress falls on -tia-:

• con-fron-TIA-mo

That is typical for this verb form. If you want to say it carefully:

• con as in cone without the final English glide
• fron
• tia sounding like tya
• mo

Hearing native audio is especially helpful here, because Italian vowel sounds are cleaner and shorter than in English.