one of the seven angels who had the seven bowls
This is one of the seven angels which John saw earlier as a great and marvelous sign (Rev. Rev. 15:1+) which were given seven golden bowls of the wrath of God (Rev. Rev. 15:7+). These bowls were poured out in the previous chapter. Since this angel shows John the woman, Babylon (Rev. Rev. 17:18+), perhaps this is the angel who poured out the seventh bowl during which Babylon was destroyed (Rev. Rev. 16:17-19+).
Come, I will show you
The same phrase is used later, probably by the same angel, when John is shown the Lambs wife: Come, I will show you the bride, the Lambs wife (Rev. Rev. 21:9+). The Great Harlot of this chapter is to be contrasted with both the Lambs wife and the woman of Revelation Rev. 12:1+. See A Virgin and a Harlot and Babylon and the New Jerusalem.
The Great Harlot is associated with Babylon (Rev. Rev. 17:5+, Rev. 17:18+; Rev. 18:21+ ; Rev. 19:2+ ). The prophets foretold the judgment which would come against Babylon. Both Isaiah and Jeremiah devote major passages to this topic which are essential background to an understanding of this chapter (Isa. Isa. 13:1, Isa. 14:1, Isa. 47:1; Jer. Jer. 50:1, Jer. 51:1). As we have seen before, prophecies in the OT often contain a mix of near-term and far-future predictions. In the case of the prophesied destruction of Babylon, the near-term aspects were fulfilled in the capture of Babylon by Cyrus (Dan. Dan. 5:30-31), but the city of Babylon has never been destroyed as predicted by the far-future aspects of Isaiahs and Jeremiahs prophecies. See The Destruction of Babylon. She is to be judged because she has corrupted the earth with her fornication and shed the blood of Gods servants (Rev. Rev. 17:6+; Rev. 19:2+).
the great harlot
She is great in the sense of having a dominant role in spiritual idolatry throughout history. In her is found the origin of all other daughter harlots (Rev. Rev. 17:5+), for she predated them and begot (influenced) them. Her harlotry speaks of her abominable practices and spiritual idolatry. See The Great Harlot.
who sits on many waters
The description of the woman shown John includes many aspects which are similar to that of Babylon at the time of Isaiah and Jeremiah. Jeremiah says concerning Babylon: O you who dwell by many waters, abundant in treasures, your end has come (Jer. Jer. 51:13a). Yet there are also differences. During the time of Jeremiah, Babylon resided by numerous waters: Babylon was surrounded by the Euphrates, which divided to form many islands, and a large lake was nearby.1 Nebuchadrezzars Babylon was the largest city in the world, covering 2,500 acres (1,000 hectares). The Euphrates, which has since shifted its course, flowed through it, the older part of the city being on the east bank.2 The Great Harlot now sits on (ἐπὶ [epi] ) many waters which are peoples, multitudes, nations, and tongues (Rev. Rev. 17:15+). This speaks of both her influence and support, no longer restricted to the plain of Shinar (Gen. Gen. 10:10; Gen. 11:2; Dan. Dan. 1:2; Zec. Zec. 5:11), but now extending throughout the world. The Great Harlot seen by John influences a much wider realm than Babylon of Old. Her influence was scattered worldwide with the introduction of languages in the judgment of Babel (Gen. Gen. 11:9). The waters upon which she sits are the waters from which the first Beast arose (Rev. Rev. 13:1+).