http://livingtheway.org/dthangel.html
Second Kings 19:35 describes an angel putting to death 185,000 Assyrians who had invaded Israel.
Exo 12:23 For the LORD will pass through to smite the Egyptians; and when he seeth the blood upon the lintel, and on the two side posts, the LORD will pass over the door, and will not suffer the destroyer to come in unto your houses to smite you.
Even in the KJV, verse 23 reads: "For the LORD will pass through to smite the Egyptians; and when he seeth the blood upon the lintel, and on the two side posts, the LORD will pass over the door, and will not suffer the destroyer [Hebrew shachath, Strong’s #7843] to come in unto your houses to smite you."
The Hebrew word shachath, translated into the noun "destroyer," is actually a verb! It is most often translated in the KJV as the verbs "destroy," or "corrupt," but also a few times as the nouns "destroyer," "corrupter," "waster," "spoilers," etc.
Now let’s look more closely at shachath. As a verb, it means "to decay; to mar; to destroy, devastate; to ruin...; to kill...; to harm...; to violate; to injure; to act wickedly...; (as a subst.) the destroying angel". In context, we might understand that Yahweh sent, not an angel to destroy, but the destruction itself! We might get the picture by reading verse 23 as, "When the LORD goes through the land to strike down the Egyptians, he will see the blood on the top and sides of the door-frame and will pass over that doorway, and he will not permit the destroying to enter your houses and strike you down." The "-ing" ending shows the use of a gerund in English, and also shows us how the verb "to destroy" can be used as a noun.
There is no such thing as a death angel, but God can send out his angels to destroy that of the wicked like in 2 Samuel 24:12-17 for one example.