One of the seven capital sins. Must be transmuted into its pure form: love, which is related to Mars (Samael). In Buddhism, anger (hate, aggression) is depicted as one of the three core defects upon which the entire Wheel of Samsara rotates. According to the Paramitas, anger is the chief obstacle in the development of patience (ksanti).

“There are three gates to self-destructive hell: lust, anger, and greed.” - Bhagavad Gita 16.21

Finding its fuel in the foul state of mind
That arises from its bringing about things I don’t want
And its preventing what I wish,
Anger, once enflamed, destroys me. - Bodhicharyavatara by Shantideva

Why, sir, do you get angry at someone who is angry with you?
What are you going to gain by it?
How is he going to lose by it?
Your physical anger brings dishonor on yourself;
Your mental anger disturbs your thinking.
How can the fire in your house burn the neighbor’s house
Without engulfing your own? - Hinduism. Basavanna, Vachana 248

“The psychic aggregates of anger are multiple. There is anger because of jealousy, because of hatred, because of frustrated desires, because of selfish monetary motives, because of disputed matters, because of terror, or because of various states of spirit, mind, body, and tongue, etc... Anger is associated with many psychic aggregates. The angry one fails in the Great Work of the Father.” - The Pistis Sophia Unveiled

“One needs serenity in order to have clairvoyance. In order to see in the Internal Worlds, one has to not allow oneself to be driven by anger, because anger destroys the frontal chakra. Therefore, serenity is required.” - The Initiatic Path in the Arcana of Tarot and Kabbalah

“Anger is the violent outcome of frustrated desire... Anger, rancor, and hatred are distinct forms of desire that are transmuted into supreme sweetness, infinite pardon, and supreme love.” - Fundamental Notions of Endocrinology & Criminology