אֵ֣ת כְּדָרְלָעֹ֜מֶר מֶ֣לֶךְ עֵילָ֗ם וְתִדְעָל֙ מֶ֣לֶךְ גּוֹיִ֔ם וְאַמְרָפֶל֙ מֶ֣לֶךְ שִׁנְעָ֔ר וְאַרְי֖וֹךְ מֶ֣לֶךְ אֶלָּסָ֑ר אַרְבָּעָ֥ה מְלָכִ֖ים אֶת־הַחֲמִשָּֽׁה׃
מיט כּדָרלעומֶר דעם מלך פֿון עֵילָם, און תִּדעָל דעם מלך פֿון גױִם, און אַמרָפֿל דעם מלך פֿון שִנעָר, און אַריאָך דעם מלך פֿון אֶלָסָר; די פֿיר מלכים אַקעגן די פֿינף.
Rashi
'ארבעה מלכים וגו FOUR KINGS [AGAINST THE FIVE]— and yet the fewer were victorious; this statement is expressly made to tell you how powerful they were, and yet Abraham did not refrain from pursuing them.
Chizkuni
כדרלעמר, he is mentioned first at this point as he was the cause of the entire war.
Siftei Chakhamim
Yet, the fewer ones were victorious. Rashi is answering the question: Why does it need to state, “Four kings”? We see that they were four! Thus he explains [that it comes to teach]: “Yet ... Avraham did not refrain...”