Maoz Tzur: Last stanza

Question

I have been to various Shuls over Chanukah and they say Maoz Tzur but they don’t say the last stanza. I asked and they say we don’t say it. What would be a reason not to say it? Don’t we want revenge on our enemies as we make a reference in Av Harachamim before Musaf Amida?

The last stanza reads (see Wikipedia):

Hebrew	English
חֲשׂוֹף זְרוֹעַ קָדְשֶׁךָ וְקָרֵב קֵץ הַיְשׁוּעָה	O bare Your holy arm and bring the end of salvation.
נְקֹם נִקְמַת עֲבָדֶיךָ מֵאֻמָּה הָרְשָׁעָה	Wreak vengeance upon the wicked nation, On behalf of your faithful servants.
כִּי אָרְכָה הַשָּׁעָה וְאֵין קֵץ לִימֵי הָרָעָה	For deliverance has too long been delayed; And the evil days are endless.
דְּחֵה אַדְמוֹן בְּצֵל צַלְמוֹן הָקֵם לָנוּ רוֹעִים שִׁבְעָה	O Reject the enemy into the shadows of idolatry, and set up for us the seven shepherds.

Av Harachamim:

יִזְכְּרֵם אֱלהֵינוּ לְטובָה עִם שְׁאָר צַדִּיקֵי עולָם. וְיִנְקום לְעֵינֵינוּ נִקְמַת דַּם עֲבָדָיו הַשָּׁפוּךְ. כַּכָּתוּב בְּתורַת משֶׁה אִישׁ הָאֱלהִים. הַרְנִינוּ גויִם עַמּו כִּי דַם עֲבָדָיו יִקּום וְנָקָם יָשִׁיב לְצָרָיו וְכִפֶּר אַדְמָתו עַמּו: וְעַל יְדֵי עֲבָדֶיךָ הַנְּבִיאִים כָּתוּב לֵאמר. וְנִקֵּיתִי דָּמָם לא נִקֵּיתִי וַיהוָה שׁכֵן בְּצִיּון: וּבְכִתְבֵי הַקּדֶשׁ נֶאֱמַר לָמָּה יאמְרוּ הַגּויִם אַיֵּה אֱלהֵיהֶם. יִוָּדַע בַּגּויִם לְעֵינֵינוּ נִקְמַת דַּם עֲבָדֶיךָ הַשָּׁפוּךְ: וְאומֵר, כִּי דורֵשׁ דָּמִים אותָם זָכָר לא שָׁכַח צַעֲקַת עֲנָוִים: וְאומֵר, יָדִין בַּגּויִם מָלֵא גְוִיּות מָחַץ ראשׁ עַל אֶרֶץ רַבָּה. מִנַּחַל בַּדֶּרֶךְ יִשְׁתֶּה עַל כֵּן יָרִים ראשׁ:

May our Lord remember them for good together with the other righteous of the world and may He redress the spilled blood of His servants as it is written in the Torah of Moses the man of God: "O nations, make His people rejoice for He will redress the blood of His servants.He will retaliate against His enemies and appease His land and His people". And through Your servants, the prophets it is written: "Though I forgive, their bloodshed I shall not forgive When God dwells in Zion" And in the Holy Writings it says: "Why should the nations say, 'Where is their God?'"Let it be known among the nations in our sight that You avenge the spilled blood of Your servants. And it says: "For He who exacts retribution for spilled blood remembers them He does not forget the cry of the humble".And it says:"He will execute judgement among the corpse-filled nations crushing the rulers of the mighty land;from the brook by the wayside he will drink then he will hold his head high.

Answer 1

There are various theories, why the last stanza is not universally sung. The first is that it is a later addition (see this article by R' Apple and also Wikipedia), which is supported by the fact that it is not included in the מרדכ"י acrostic and it contains references to later events. The last stanza is also brought in the Kitzur Shenei Luchot haBerit by R' Yechiel Mikhal Epstein (d. 1706):

מצאתי כתוב מאחר שהשיר של מעוז צור אינו קאי רק על ג' מלכיות, בבל מדי יון, אבל מלכות רביעי, גלות אדום וישמעאל לא נזכר בו כלום. על כן התקינו איזה חרוזות המדברים על גאולת מגלות הזה, שיאמר אחר השיר מעוז בניגון מעוז צור.‏

I have found written that because the poem Maoz Tzur does only discuss three kingdoms, Babylonia, Persia and Greece, but the fourth kingdom, the exile of Edom and Yishmael is not mentioned at all. Therefore these stanzas were instituted that speak about the redemption of this exile, which is said after the poem Maoz [Tzur] using the melody of Maoz Tzur.

Here he lists other later stanzas attributed to R' Moses Isserles and other rabbanim. However, the mentioned article and the Yekke prayer book Tefilat Yeshurun suggest another reason, namely that it was deleted due to censorship (see also Hebrew Wikipedia). The Encyclopedia Judaica (Vol. 13 p. 496) assumes that the initials ח"זק in the last stanza belong to the מרדכ"י acrostic, which was a common feature of medieval liturgical poems.

Avraham Frankl also rejects the former hypothesis and brings evidence (pp. 15–16) that the last verse forms an integral part of the poem. Besides the otherwise missing fourth kingdom and reference to redemption, he argues that he is not aware of other poems, where a stanza with an acrostic was appended. The meter and the rhyming structure also match the first verses in contrast with the other ones mentioned in the Kitzur Shelah, further supporting his claim.