John the Apostle
Revelation 9:11ESV·traditional attribution

They have as king over them the angel of the bottomless pit. His name in Hebrew is Abaddon, and in Greek he is called Apollyon.

Matthew Henry Presbyterian @wholebiblehenry

Upon the sounding of this trumpet, the things to be observed are, 1. A star falling from heaven to the earth. Some think this star represents some eminent bishop in the Christian church, some angel of the church; for, in the same way of speaking by which pastors are called stars, the church is called heaven; but who this is expositors do not agree.

Commenting on Revelation 9:1-12

John Gill Reformed Baptist @doctorgill

And they had a king over them,.... Which natural locusts have not, Pro 30:27; by whom is meant the false prophet Mahomet, who was at the head of the Saracens, and led them on to commit the outrages they did; and is believed in by the Turks to this day, as the great prophet of God, and by them preferred to all prophets, not only...

Albert Barnes Presbyterian @notesbybarnes

Verse 11. And they had a king over them. A ruler who marshalled their hosts. Locusts often, and indeed generally, move in bands, though they do not appear to be under the direction of any one as a particular ruler or guide.