Massacres in the Tanakh

1. Avimelech vs. His Brothers in Judges 9

ה  וַיָּבֹא בֵית-אָבִיו, עָפְרָתָה, וַיַּהֲרֹג אֶת-אֶחָיו בְּנֵי-יְרֻבַּעַל שִׁבְעִים אִישׁ, עַל-אֶבֶן אֶחָת; וַיִּוָּתֵר יוֹתָם בֶּן-יְרֻבַּעַל, הַקָּטֹן--כִּי נֶחְבָּא.  {ס}

5 And he went unto his father's house at Ophrah, and slew his brethren the sons of Jerubbaal, being threescore and ten persons, upon one stone; but Jotham the youngest son of Jerubbaal was left; for he hid himself.

2. Doeg vs. the Priests of Nov in I Samuel 22.

יח  וַיֹּאמֶר הַמֶּלֶךְ, לדויג (לְדוֹאֵג), סֹב אַתָּה, וּפְגַע בַּכֹּהֲנִים; וַיִּסֹּב דויג (דּוֹאֵג) הָאֲדֹמִי, וַיִּפְגַּע-הוּא בַּכֹּהֲנִים, וַיָּמֶת בַּיּוֹם הַהוּא שְׁמֹנִים וַחֲמִשָּׁה אִישׁ, נֹשֵׂא אֵפוֹד בָּד.	18 And the king said to Doeg: 'Turn thou, and fall upon the priests.' And Doeg the Edomite turned, and he fell upon the priests, and he slew on that day fourscore and five persons that did wear a linen ephod.
יט  וְאֵת נֹב עִיר-הַכֹּהֲנִים, הִכָּה לְפִי-חֶרֶב, מֵאִישׁ וְעַד-אִשָּׁה, מֵעוֹלֵל וְעַד-יוֹנֵק; וְשׁוֹר וַחֲמוֹר וָשֶׂה, לְפִי-חָרֶב.	19 And Nob, the city of the priests, smote he with the edge of the sword, both men and women, children and sucklings, and oxen and asses and sheep, with the edge of the sword.
כ  וַיִּמָּלֵט בֵּן-אֶחָד, לַאֲחִימֶלֶךְ בֶּן-אֲחִטוּב, וּשְׁמוֹ, אֶבְיָתָר; וַיִּבְרַח, אַחֲרֵי דָוִד.	20 And one of the sons of Ahimelech the son of Ahitub, named Abiathar, escaped, and fled after David.

3. Assalya vs. the Royalty in 2 Kings 11.

א  וַעֲתַלְיָה אֵם אֲחַזְיָהוּ, וראתה (רָאֲתָה) כִּי מֵת בְּנָהּ; וַתָּקָם, וַתְּאַבֵּד, אֵת, כָּל-זֶרַע הַמַּמְלָכָה.	1 Now when Athaliah the mother of Ahaziah saw that her son was dead, she arose and destroyed all the seed royal.
ב  וַתִּקַּח יְהוֹשֶׁבַע בַּת-הַמֶּלֶךְ-יוֹרָם אֲחוֹת אֲחַזְיָהוּ אֶת-יוֹאָשׁ בֶּן-אֲחַזְיָה, וַתִּגְנֹב אֹתוֹ מִתּוֹךְ בְּנֵי-הַמֶּלֶךְ הממותתים (הַמּוּמָתִים)--אֹתוֹ וְאֶת-מֵינִקְתּוֹ, בַּחֲדַר הַמִּטּוֹת; וַיַּסְתִּרוּ אֹתוֹ מִפְּנֵי עֲתַלְיָהוּ, וְלֹא הוּמָת.	2 But Jehosheba, the daughter of king Joram, sister of Ahaziah, took Joash the son of Ahaziah, and stole him away from among the king's sons that were slain, even him and his nurse, and put them in the bed-chamber; and they hid him from Athaliah, so that he was not slain.
ג  וַיְהִי אִתָּהּ בֵּית יְהוָה, מִתְחַבֵּא שֵׁשׁ שָׁנִים; וַעֲתַלְיָה, מֹלֶכֶת עַל-הָאָרֶץ.  {פ}	3 And he was with her hid in the house of the LORD six years; and Athaliah reigned over the land. {P}

I find it very interesting that there is always the lone survivor. Yotam, Evyatar and Yoash are all lone survivors. Yotam and Yoash are hidden while Evyatar actively escapes.

I'm not sure what the deeper message is here (or if there is one), but I do find the consistency interesting.