Wisdom (488): A Mujahid who is a martyr in the way of God does not deserve more reward than a person who remains pure while having power and authority. Is it unlikely that one of the pure angels will become an angel?

The Mujahid who is martyred in the way of God does not deserve more reward than the person who remains pure while having power and authority. Is it unlikely that one of the pure angels will become an angel?