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
And they had a king over them, which is the angel of the bottomless pit, whose name in the Hebrew tongue is Abaddon, but in the Greek tongue hath his name Apollyon.
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”.