עָשׂ֣וּ מִלְחָמָ֗ה אֶת־בֶּ֙רַע֙ מֶ֣לֶךְ סְדֹ֔ם וְאֶת־בִּרְשַׁ֖ע מֶ֣לֶךְ עֲמֹרָ֑ה שִׁנְאָ֣ב ׀ מֶ֣לֶךְ אַדְמָ֗ה וְשֶׁמְאֵ֙בֶר֙ מֶ֣לֶךְ צביים [צְבוֹיִ֔ים] וּמֶ֥לֶךְ בֶּ֖לַע הִיא־צֹֽעַר׃
Krieg mit Bera, König von Sodom, Birscha, König von Gomorrha, Schinab, König von Admah, Schemeber König von Zebojim, und mit dem Könige von Bela, dem heutigen Zoar.
Rashi on Genesis
ברע BERA —Evil (רע) towards God and evil towards mankind (Midrash Tanchuma, Lech Lecha 8).
Ramban on Genesis
AND THE KING OF BELA. The reason [why Scripture does not mention his name as it does with the kings of Sodom, et al], is that he ruled over a small city with few men in it and he had no generally recognized reputation.
Radak on Genesis
עשו מלחמה, now the Torah tells of the battle between them in the valley of Sidim. The fact that there had been previous wars resulting in the five kings becoming subservient to the four kings is mentioned only as a backdrop to this war that prompted Avram’s involvement.