Complex sentence: Vader fights Obi-Wan in a lightsaber duel that ends with Obi-Wan dismembering him; he gets burned by a volcanic river as Obi-Wan leaves him to die.
Split into simpler sentences: Vader fights Obi-Wan in a lightsaber duel that ends with Obi-Wan dismembering him. Vader is burned by a volcanic river and Obi-Wan leaves him to die.