No he was not a devil. He was a human.
What's the worst thing the Bible says the Devil ever did, and that's in the New Testament because basically the Devil is a Christian bogeyman but they got from me wrongings. According to the story, Jesus was in the desert with nothing but a jug of wine for 40 days. During this period, the Devil approached him one day and said, hey Jesus, are you hungry? Can't you just make yourself some bread? The end.
According to the Bible that is the evil that the Devil did. He told Jesus to bake himself some bread because doing nothing but drinking wine for 40 days out in the desert is really not a good thing to do. Bread. The Devil is evil because he said have some bread.
The Bible is full of killing, war, killing, raping, killing, more war, more killing... That's what it's about. But the Devil is bad because he told Jesus to go have himself a slice of bread. Let that sink in.