I have come to the conclusion that the most powerful apologetics argument that a Catholic can make against Protestantism is that their Sunday Liturgy is actually man-made and thus blatant idolatry. Let me explain this more.
The most important duty a human has, regardless even of whether they are a Christian or not, is to worship God. This should be - without a doubt - an obvious truth that everyone can agree upon. Given this, a person must not only worship God, they must do so properly, i.e., they must worship as God has instructed them to do. This means that Liturgy requires divine revelation, because otherwise the person is "worshiping" God based on what sounds good to their human mind...but there is a word for worshiping according to what sounds good to you: it's called idolatry. So the only way to escape idolatry is to worship according to how God has divinely revealed it. Which leads us to the key problem which all Protestants face.
The key problem that all Protestants face is that nowhere in Scripture is the Christian Liturgy laid out. Nowhere. Many people think it is acceptable to make up their own liturgy as long as they are singing a Psalm or reading a Bible passage, but this is not Liturgy, it is making up your own liturgy (and thus a form of idolatry). Ask a Protestant if what they are doing on Sunday is expressly commanded in the Bible and they will fumble around. They wont have an answer. Because the Bible doesn't give them an answer. The Protestant then needs to be told that the only way they can avoid being guilty of Idolatry this upcoming Sunday is for them to cease doing what they do on Sunday. Any Protestant serious about the Bible must face this reality.
But the Catholic is not in this bind because the Catholic Mass does come from divine revelation: it comes from Jesus through the Apostles, through inspired oral tradition. Sola Scriptura is instantly disproved. This argument is the apologetics equivalent of kryptonite to a Protestant. They melt to the floor as soon as you introduce it to them. I've used it on many Protestants with great success. I've even had some Protestants admit that since the Bible doesn't tell us what the Christian Liturgy is supposed to look like, then Christians don't technically have to worship on Sunday and don't have to worship at all. That's the effectiveness that I'm talking about.
When it comes to what Scripture actually says about the Christian Liturgy, the strongest passage is 1 Corinthians 10:14-22,
Therefore, my beloved, flee from idolatry. The cup of blessing that we bless, is it not a participation in the blood of Christ? The bread that we break, is it not a participation in the body of Christ? Consider the people of Israel: are not those who eat the sacrifices participants in the altar? What do I imply then? I imply that what pagans sacrifice they offer to demons and not to God. I do not want you to be participants with demons. You cannot drink the cup of the Lord and the cup of demons. You cannot partake of the table of the Lord and the table of demons.
In this beautiful passage we Paul equating man-made worship with idolatry. As the Council of Trent says, quoting this passage, Paul clearly shows the Christian Liturgy is in its essence a Sacrifice upon an Altar, contrasted here to the Pagan Table-Altar (see Mal 1:7). It is no surprise that Protestants 'dont see' this passage when they read the Bible, because in rejecting the Sacrifice of the Mass, they unwittingly threw out Divine Worship and instead replaced true worship with a Bible study. It is idolatrous nonetheless because it parades around as worship when in reality it isn't. As I've said before, Protestants do not worship God.