Complex sentence: This bloodthirsty Skull Squadron tracker is normally cold and methodical, but when he's on the verge of a strike, he goes into a state of frenzied excitement, which makes escape from his gun sights almost impossible.
Split into simpler sentences: This bloodthirsty Skull Squadron tracker is normally cold and methodical. But when he's on the verge of a strike, he goes into a state of frenzied excitement... which makes escape from his gun-sights almost impossible.