Complex sentence: Following the complete destruction of his home town Coast City by the villain Mongul, Hal Jordan descended into madness, destroying the Green Lantern Corps, killing his friend Kilowog and all of the Guardians except for Ganthet.
Split into simpler sentences: Following the complete destruction of his home town Coast City by the villain Mongul, Hal Jordan descends into madness. Jordan went on a rampage, destroying the Green Lantern Corps, killing his friend Kilowog and all of the Guardians except for Ganthet.