Complex sentence: The Joker sets fire to the mob's money (burning Lau alive in the process), kills the Chechen and, not wanting Reese's revelation to interfere with his plans, threatens to destroy a hospital unless someone kills Reese.
Split into simpler sentences: The Joker sets fire to the mob's money, burning Lau alive in the process, and kills the Chechen. Not wanting Reese's revelation to interfere with his plans, the Joker threatens to destroy a hospital unless someone kills Reese.