Charles Ellicott Commentary Isaiah 59:18

"According to their deeds, accordingly he will repay, wrath to his adversaries, recompense to his enemies; to the islands he will repay recompense." — Isaiah 59:18 (ASV)

To his adversaries ... —The judgment is generally against all, in Israel or outside it, who come under this description. The word “islands” is used, as elsewhere, for far-off lands. The words point to every such judgment, from that of Cyrus to the great final day.