The Angel of Death and Hashem
The angel of death refers to King Gog from the land of Magog, prophesied by Yechezkel (Yechezkel 38:8, 16, 10). The Targum refers to Yishmael, who shall kill many nations (see further Zechariah 11 to 14). He is called the Angel of Death because the gematria of malach hamaves equals “He is the great king Gog from the land of Magog.” Hashem, the Holy One, blessed be He, shall kill Gog and all his myriad minions. At that time the verses will be fulfilled: “And they shall know that I am Hashem your G-d,” and “I gathered them unto their land and I shall leave none of them there behind.” This did not occur after the Babylonian exile, when, as stated in Nechemia 7, only 42,360 returned. It fulfills the prophecy of Zechariah 13: “And on that day, said the Lord of Hosts, I shall cut down the idols from the land, and their memory shall cease, and their prophets as well, and the spirit of impurity shall I remove from the land; death shall be swallowed up forever, and on that day Hashem and His Name shall be one.” Amen, may it be His will.
Source: Peirush on Chad Gadya, Haggadah Shel Pesach (Yechezkel 38; Zechariah 11-14; Nechemia 7)