Avalokiteshvara — “the lord who looks down” — is the archetypal bodhisattva of Karuna, compassion. In Chinese traditions he becomes Guanyin (often depicted as feminine); in Japanese, Kannon; in Tibetan, Chenrezig.
The Heart Sutra is spoken by Avalokiteshvara to Shariputra. The 25th chapter of the Lotus Sutra is a whole sutra in praise of Avalokiteshvara’s saving activity. The mantra Om Mani Padme Hum invokes his compassionate presence.
In Tibetan Buddhism, the line of the Dalai Lama is held to be an emanation of Chenrezig — compassion incarnating again and again for the sake of suffering beings.