It is possible for a being to be perfectly good, but it is not possible any being to be perfectly evil.
Explanation
Jesus lived a perfect life. He was literally pure, incarnate good. Yet, there is not being that is perfectly evil. There have been meny terrible men in history who killed hundred, thousands, and millions. There have been monsters. Yet, each of these men showed some kindness. Many of them took care of their families and friends, bought gifts, and showed love to others. Even psychotics and sociopaths do good from time to time.
Even Satan, the author of evil, was at one time the most beautiful of angels. He might entice people away from God and lead them toward eternal damnation, yet even he often does so through the tempting allure of good things.