Satan invented evil.
The Bible asserts that GOD created everything "very good," meaning that it was completely righteous and free from sin.
Satan was also created as holy, righteous, and free from sin.
Sin is that which is inconsistent with GOD's character and will. GOD created the world to operate in a particular manner, yet He gave free will to the beings He created to rule over His creation, angels and humans.
If everything was initially created as good, holy, and sin-free, then sin had to originate somewhere. The Bible claims that Satan invented sin and did evil "from the beginning."
8 The one who does what is sinful is of the devil, because the devil has been sinning from the beginning.
(1 John 3:8 NIV)
42 Jesus said to [the Jews], “If God were your Father, you would love me, for I have come here from God. I have not come on my own; God sent me. 43 Why is my language not clear to you? Because you are unable to hear what I say. 44 You belong to your father, the devil, and you want to carry out your father’s desires. He was a murderer from the beginning, not holding to the truth, for there is no truth in him. When he lies, he speaks his native language, for he is a liar and the father of lies.
(John 8:42-44 NIV)