This is a very common misconception but in Christianity there is no angel of death. Death is just that. Death. Although many angels have been given the task of killing, and there are some well known ones. There is no supernatural being in charge of taking our life, we die when it’s our time through stupidity on our part or the part of others, through accident or through illness and old age.
Yes there was an angel sent to kill the first born in Egypt (Uriel) but he is also a cherub who guards the tree of life and helped to bury Adam and Abel in paradise.
Samael is linked strongly to Cain and is thought to be the angel who brought the desire to kill to humans but he had other tasks as well as being one of the 7 angels that will blow their trumpets at the time of the apocalypse. Samael’s name translates to ‘poison of God’. Samael is also considered to be the patron saint of Edom. Samael is still considered to be one of the heavenly host even though he condones human sin. And if we look at Jewish lore According to The Ascension of Moses Samael is also mentioned as being in 7th Heaven:
In the last heaven Moses saw two angels, each five hundred parasangs in height, forged out of chains of black fire and red fire, the angels Af, “Anger,” and Hemah, “Wrath,” whom God created at the beginning of the world, to execute His will. Moses was disquieted when he looked upon them, but Metatron embraced him, and said, “Moses, Moses, thou favorite of God, fear not, and be not terrified,” and Moses became calm. There was another angel in the seventh heaven, different in appearance from all the others, and of frightful mien. His height was so great, it would have taken five hundred years to cover a distance equal to it, and from the crown of his head to the soles of his feet he was studded with glaring eyes. “This one,” said Metatron, addressing Moses, “is Samael, who takes the soul away from man.” “Whither goes he now?” asked Moses, and Metatron replied, “To fetch the soul of Job the pious.” Thereupon Moses prayed to God in these words, “O may it be Thy will, my God and the God of my fathers, not to let me fall into the hands of this angel.”
But looking back at the christian bible, Samael is mentioned in the Apocryphon of John, found in the Nag Hammadi library, Samael is the third name of the demiurge, whose other names are Yaldabaoth and Saklas. In this context, Samael means “the blind god”, the theme of blindness running throughout gnostic works. His appearance is that of a lion-faced serpent. In the Origin of the World in the Nag Hammadi library texts, he is also referred to as Ariael, the Archangel of Principalities.
So all in all, there are differing opinions on who the angel of death is. But in accordance with scripture, there are many angels given the tasks of killing at different times and these angels also have different tasks at other points.