Complex sentence: When Spider-Man is aided by Thor and S.H.I.E.L.D., Executioner leads the hunters into attacking the S.H.I.E.L.D. Helicarrier, but before he can deliver the finishing blow, the sun sets, ending the hunt.
Split into simpler sentences: When Spider-Man is aided by Thor and S.H.I.E.L.D., Executioner leads the hunters into attacking the S.H.I.E.L.D. Helicarrier. Before Executioner can deliver the finishing blow, the sun sets, ending the hunt.