Complex sentence: Dionysius I or Dionysius the Elder (ca.432--367 BC,), tyrant of Syracuse, conquered several cities in Sicily and southern Italy, opposed Carthage's influence in Sicily and made Syracuse the most powerful of the Western Greek colonies.
Split into simpler sentences: Dionysius I or Dionysius the Elder (ca.432--367 BC,) was a Greek tyrant of Syracuse, in what is now Sicily, southern Italy. He conquered several cities in Sicily and southern Italy opposed Carthage's influence in Sicily and made Syracuse the most powerful of the Western Greek colonies.