Complex sentence: Hitman first appeared during Garth Ennis's run on "The Demon" during the "Bloodlines" crossover, and subsequently appeared in two further arcs before the series was cancelled.
Split into simpler sentences: Hitman first appeared during Garth Ennis's run on "The Demon". He first appeared during the "Bloodlines" crossover, and subsequently appeared in two further arcs before the series was cancelled.