Complex sentence: In December 2001, the two championships were unified at Vengeance, where Stone Cold Steve Austin defeated Kurt Angle to retain the WWF Championship, while Chris Jericho defeated The Rock for the World Championship.
Split into simpler sentences: In December 2001, the two championships were unified at Vengeance. At the event, Stone Cold Steve Austin defeated Kurt Angle to retain the WWF Championship, while Chris Jericho defeated The Rock for the World Championship.