Revelation 9:11

They were ruled by a king, the angel of the Abyss. His name in Hebrew is Abaddon, and in Greek it is Apollyon.

Berean Standard Bible (BSB)

They have over them as king the angel of the abyss. His name in Hebrew is “Abaddon,” but in Greek, he has the name “Apollyon.”

World English Bible (WEB)

And{G2532} they had{G2192}{(G5719)} a king{G935} over{G1909} them{G848}, which is the angel{G32} of the bottomless pit{G12}, whose{G846} name{G3686} in the Hebrew tongue{G1447} is Abaddon{G3}, but{G2532} in{G1722} the Greek tongue{G1673} hath{G2192}{(G5719)} his name{G3686} Apollyon{G623}.

Strong's King James

(11) They have as king upon them, the angel of the abyss, his name in Hebrew is Abaddon (destruction) and in Greek has the name Apollyon (Destroyer).

The F.O.G*

[11] Their king was the angel of the Abyss—in Hebrew called Abaddon, in Greek, Apollyon. Both names mean "Destroyer," revealing his essence as an agent of destruction opposed to God's creative and redemptive purposes.

The F.O.G Paraphrase

and they have over them a king—the messenger of the abyss—a name is to him in Hebrew, Abaddon, and in the Greek he hath a name, Apollyon.

Young's Literal Translation