Complex sentence: Karna as an adult expressly stated his loyalty to his commoner foster mother, as opposed to his royal birth mother Kunti who had abandoned him soon after he was born, he is sometimes called "Radheya", meaning "Radha's son".
Split into simpler sentences: Karna as an adult express loyalty towards his foster mother as opposed to his royal birth mother Kunti who had abandoned him soon after birth. Hence, he is sometimes called "Radheya", meaning "Radha's son".