O my Jesus, forgive us our sins! Save us from the fires of Hell! Lead all souls to Heaven, especially those in most need.

Or

O my Jesus, forgive us our sins! Save us from the fires of Hell! Lead all souls to Heaven, especially those in most need of Thy mercy].

I have heard the first one was correct and guessed the last sentence was referring to those souls in Purgatory.

What about this:

O My Jesus, forgive us our sins!  Save us from the fires of Hell!  Lead all souls to Heaven, especial those souls in Purgatory who are most forgotten.

Another example"

O My Jesus, forgive us our sins and save us from the Fires of Hell!  Lead all souls to Heaven but most especially the abandoned souls in Purgatory.

http://www.holyromancatholicchurch.org/articles/FatimaPrayer.htm

The True Fatima Prayer

"O my Jesus, forgive us and save us from the fire of Hell, lead all poor
souls toward Heaven, especially those who are most in need."

I ran across this article on the Web and I confirmed the stated words of The Blessed Mother as recorded by Sr. Lucia on a different Portuguese website that had photocopies from her diary (See the attachments). It makes one wonder how such a blatant mistranslation could occur and to what end. You would think that when it came to translating the words of the Blessed Virgin Mary, you would take exquisite care in the translation. The effects of the mistranslation as summarized by Br. Bugnolo are especially distressing . My family and I now say the Fatima Prayer as Our Lady intended. --HRCC

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In English this prayer is commonly called, "The Fatima Prayer"; in
Portuguese, "O meu Jesus" prayer.

--The Portuguese Text is sometimes given as:

O meu Jesus, perdoai-nos e livrai-nos do fogo do inferno. Levai as almas
todas para o Ceu, e socorrei principalmente aquelas que mais precisarem.


**But the actual words of Our Lady, according to Sr. Lucia are:

O meu Jesus, perdoai-nos e livrai-nos do fogo do inferno, levai as alminhas
todas para o Ceu, principalmente aquelas que mais precisarem".

Even if you have not studied Portuguese, you can examine both versions and
find the textual differences.


--In English we commonly use the translation of the first version of the
text, cited just above, which is:

O my Jesus, forgive us our sins, save us from the fires of Hell. Lead all
souls to Heaven, especially those most in need of Thy mercy.


The more accurate version would be the translation of Our Lady's actual
words, as Sr. Lucia reports them:

** "O my Jesus, forgive us and save us from the fire of Hell, lead all poor
souls toward Heaven, especially those who are most in need." **

literally "O my Jesus, you pardon us, you exempt us of the fire of the hell;

you take little souls all for the Sky, mainly those that more to need. "
 



This would be more theologically accurate, since there is ontologically
only 1 fire of Hell, not "fires of Hell", and the poor souls are not only
lead "to Heaven" but up ever closer "toward Heaven" through the various
stages of purification. And, the needs of the poor souls are not only
those respecting God's "mercy", but of our prayers and sacrifices and merits.

Finally, the punctuation of the actual text is more theologically accurate,
since it contains 3 petitions: forgiveness, salvation, and leading of the
poor souls: we pray for the first and the second for ourselves; but the
first so that we may merit the third for poor souls. And we pray to be
saved from the fire of Hell and for the poor souls, because according to
the Saints, it is the same fire in Hell and purgatory.


Sincerely in Christ,

Br. Alexis Bugnolo"
 

----------------------------------------------------------------------------------------------

and also......

 

I would point out that this English translation is not exactly correct;
because the Portuguese does not say "souls", but "little souls", a term of
endearment among Portuguese Catholics for the souls in Purgatory, equivalent
to our phrase "poor souls". The the context of the phrase refers to the
deliverance of all souls from purgatory into heaven; and thus never
signified universal salvation.

I believe that there are a few articles on this point on the web somewhere.

Sincerely in Christ,

Br. Alexis Bugnolo
The Franciscan Archive"

Copy of the Fatima Prayer in Sr. Lucia's handwriting

Copy of the Fatima Prayer in Portuguese

 

In Portuguese the Novus Ordo Catholics use ending "in most need of Thy Divine Mercy".  Traditionalists refuse to make use of this prayer because it is a reference to Sister Faustina.  The English version is most probably a similar adaptation which should be disregarded as well.  How these modifications spread across various languages and cultures is puzzling.

My sedevacantist friend prays a different version of the Fatima prayer in his Rosary. He says the true prayer is "O my Jesus, forgive us our sins. Save us from the fires of hell. Have pity on the poor souls in purgatory, especially those most abandoned." He believes the prayer that most pray is a modernist replacement of the true Fatima prayer meant to lead people into believing in universal salvation (asking Our Lord to lead "all souls" to heaven).

My sedevacantist friend prays a different version of the Fatima prayer in his Rosary. He says the true prayer is "O my Jesus, forgive us our sins. Save us from the fires of hell. Have pity on the poor souls in purgatory, especially those most abandoned." He believes the prayer that most pray is a modernist replacement of the true Fatima prayer meant to lead people into believing in universal salvation (asking Our Lord to lead "all souls" to heaven).

Some SVs get a little paranoid.  Praying for the salvation of all is NOT the same thing as universal salvation.

This site gives a pretty good argument that the original prayer as intended by our Lady and understood by Sr. Lucia was for the souls of sinners, not the souls in Purgatory:

https://crc-internet.org/our-doctrine/catholic-counter-reformation/whole-truth-fatima/6-july-13/appendices-ii.html