Complex sentence: News of the despicable acts committed on Abhimanyu reached his father Arjuna at the end of the day, who vows to kill Jayadratha the very next day by sunset, and failing to do so, commit suicide by self-immolation immediately.
Split into simpler sentences: News of the despicable acts committed on Abhimanyu reached his father at the end of the day. Arjuna vows to kill Jayadratha the very next day by sunset, and failing to do so, would commit suicide by self-immolation immediately.