Radha shown here with Krishna is the most important of Krishna's many female friends. The love between Krishna and Radha, and Radha's devotion to her lover, in time became allegory for the love between Krishna the god and his followers, as well as of the follower's devotion (bhakti) to the god. In addition, the two-in-one Krishna-Radha embodies the tantric principle of the two aspects of the divine (male and female), which together form the one formless reality.
During his life on earth Krishna defeated many enemies. He slew the above mentioned king Kamsa and the snake king Kaliya, but was also victorious in his battles with the Vedic god Indra on several occasions.
He is shown here playing his trademark flute.
This description by Nitin Kumar, Executive Editor, Exotic India.
Danielou, Alain. The Myths and Gods of India: Vermont, Inner Traditions International, 1991.
Jansen, Eva Rudy. The Book of Hindu Imagery, The Gods and their symbols: Holland, Binkey Kok Publishers, 1998.