Besides there is nothing in this thread to infer that this brave young man is, or claims  to be, the Great Monarch, except for the title Sean gave it.

Indeed.  Never will understand some of the tabloid titles here.

Is there text in Book of Apocalypse inferring or stating a "great monarch" a la the Catholic prophesies is coming?

No, but there is the mention of a period of peace lasting about a generation before the arrival of Antichrist, and there's tons of private prophecy regarding the Great Monarch from some highly credible mystics.

http://www.todayscatholicworld.com/great-catholic-monarch.htm

King of France, descendant of the Capetians, with Spanish and German blood. A Bourbon? It's the only dynasty that fits there. It's a dynasty that descends from the Capetians, they are claimants to the throne of France, in turn the kings of France ultimately descend from the Franks, who were the Germans who invaded that part of the Roman Empire, and it's a dinasty with presence in Spain and currently the King of Spain is a Bourbon.

So ... perhaps this guy?

https://en.wikipedia.org/wiki/Louis_Alphonse_de_Bourbon

No, but there is the mention of a period of peace lasting about a generation before the arrival of Antichrist, and there's tons of private prophecy regarding the Great Monarch from some highly credible mystics.

http://www.todayscatholicworld.com/great-catholic-monarch.htm

While there certainly isn't anything about a Great Catholic Monarch in Scripture, are you talking about the period of peace in Apoc. 20?

And I saw seats; and they sat upon them; and judgment was given unto them; and the souls of them that were beheaded for the testimony of Jesus, and for the word of God, and who had not adored the beast nor his image, nor received his character on their foreheads, or in their hands; and they lived and reigned with Christ a thousand years. [5] The rest of the dead lived not, till the thousand years were finished. This is the first resurrection.

Father Sylvester Berry disagrees that the Peace precedes Antichrist, as Scripture plainly places it after Antichrist:

Fr. Berry, The Apocalypse of St. John, Part III, Ch. XX, pp. 189, 190

But practically all interpreters who accept these conclusions take the reign of Antichrist as a prelude to the last judgment and the end of the world. Then, contrary to the plain sense of Holy Scripture, they place the universal reign of Christ before the time of Antichrist. This, in turn, makes the chaining of the dragon a difficult problem. p.189

After the defeat of Antichrist the Gentile nations will return to the Church and the Jєωs will enter her fold. Then shall be fulfilled the words of Christ: ''There shall be one fold and one shepherd.'" Unfortunately sin and evil will not have entirely disappeared, the good and the bad will still be mingled in the Church, although the good shall predominate. After many centuries, symbolized by a thousand years, faith will diminish and charity grow cold as a result of the long peace and security enjoyed by the Church. Then Satan, unchained for a short time, will seduce many nations (Gog and Magog) to make war on the Church and persecute the faithful. These apostate nations shall be promptly overwhelmed with a deluge of fire and the Church will come forth again triumphant. The general judgment and the end of the world will then be near at hand. p. 190

As does Fr. Kramer:

Fr. Kramer, The Book of Destiny, X. 1. xx., pp. 451, 452, 453.

Verse four is impossible of logical interpretation for those who place the thousand years chronologically ahead of the reign of Antichrist, because its contents are a positive contradiction of that theory.

The martyrs who shed their blood under Antichrist shall rule the world with Christ for a thousand years. They saved the world from utter destruction by their heroism; so they shall be specially honored by their own nation. They may receive control over the elements and whatever else influences human life, as many saints have had power of intercession against diseases, misfortunes and calamities.

During the thousand years also those shall rule with Christ who have faithfully held to the teachings of the Church, kept the commandments and practiced their religion in defiance of all danger, though they may have died from other causes. The language of verse 4 permits such interpretation. They have not submitted to Antichrist nor adored him nor received the imprint of his insignia on their foreheads or hands.

They will reign from Antichrist till the end of time. This places the THOUSAND YEARS after the advent and domination of Antichrist whom their courage and constancy defeats and overthrows.

Obviously, this creates problems for the private revelations which state that the GM precedes Antichrist, as Scripture plainly testifies to the reign of peace coming after the fall of Antichrist.

Which also, in my view, creates even more problems for the MHFM view of JPII as Antichrist (again, it's compelling, but misses a lot of marks, and I have yet to hear back from MHFM about some of these points they miss); as it is clear that Antichrist will proclaim that HE is the Messiah, the Christ, not just teach heresy about all men being Jesus Christ (like JPII, who has CLEARLY promulgated Antichrist's doctrine by dissolving Christ, 1 John 4:3). But at the same time, what compels me to their thesis is that spiritual destruction on a mass scale far, far outweighs any physical destruction. It's possible they are correct in stating that the First Beast, the Red Dragon, was Soviet Communism which has given way to the Second Beast and the Harlot which is the NWO and the Novus Ordo false religion, respectively, of which the Image of the Beast (Antichrist) sits atop the Harlot. So, if the NO is the prophesied Harlot, then the Antichrist has to have either come already or is to come soon as some sort of NO prelate or Antipope (given that the Papacy is the highest office in this world).

Interestingly enough, the 3.5 years commonly attributed to the reign of the Man of Sin is interpreted by Sig. Pastorini as a limit on the length of any given persecution in Church history:

Sig. Pastorini, History of the Christian Church, p. 61-62

In these various desolate abodes the Christians, though in appearance destitute of all human succour, were nevertheless fed and supported by a special divine providence for the space of a thousand two hundred and sixty days, or three years and a half, which was the utmost duration of any of the Roman persecutions; some of which did not fill that period, none exceeded it.

I don't see a period, in recent memory surrounding the Vatican II catastrophe, that fits such a period outside of the Council itself, which lasted 3 years and 2 months; or, possibly, the suppression of the Mass with the promulgation of the Novus Ordo Missae under Paul VI in 1969, albeit there's no definite period of time I've identified pertaining to it. Although Pastorini believes that no persecution will exceed it at any time.

As for worldly events, clearly the COVID lie we've been living through for 2.5 years now would fit such a period of persecution, as all who hold the name of Christian have suffered some form of persecution through its lockdowns and mandates.

Doesn't John 5:43 mean that the Antichrist will be recognized by the Jєωs as their messiah? That has not happened yet. Also the kill of the Two Witnesses.

Some tend to take that interpretation, yes. But it could also simply mean that they will take to themselves false teachers (such as the тαℓмυdic Rabbis) or even claimants to the title of "Mosiach", like in recent years. I honestly think the Antichrist will be their Mosiach, as do others here.

As for the Two Witnesses, I've heard that some speculate that it refers to Sts. Peter and Paul (citation needed), who both died in the Roman persecutions. Others think it will be Henoch and Elijah, or even Henoch and Moses. I personally don't see anyone in Church history, especially recently, who fits the bill (which are both points against the MHFM thesis).

What about Brothers Michael and Peter Dimond? 

I have head some people throw +Lefebvre and +de Castro Mayer out there.

Well, considering they think that JPII was the Antichrist, I don't ever recall them being martyred in Rome, displayed publicly for 3 days, and then resurrecting and ascending into heaven.

I have heard the +Lefebvre and +de Castro-Mayer idea too, I think I even proposed it as a possibility the last time we talked about this subject. It's certainly plausible, from a spiritual standpoint, given their acceptance of the terms offered in the Ecclesia Dei commission as a "spiritual death" followed by a "spiritual resurrection" through their rejection of it before both dying exactly a month apart from each other (+Lefebvre March 25, 1991; de Castro-Mayer April 25, 1991). Not that I'm implying they ascended to heaven (as +Lefebvre open taught against EENS that non-Catholics can be saved in Against the Heresies, which, unfortunately, makes him a manifest heretic in the external forum given he never publicly repudiated it, although he could have privately done so before death)

This, of course, would fit better given that the spiritual persecution of the Faithful which came through the heresies and scandals of JPII, if he were the Antichrist.

As for the Great Monarch, Eric GaJєωski presents himself as the leading candidate.

Jackie Chan and Bruce Lee types in some decent numbers could shake things up in communist China and then he might be able to pull it off. He sounds like a good theoretician though.