Vengeance is a Dish Best Served Ben
When Rousseau is shot dead by hidden assassins, Alex (aka Ben's daughter) is captured by a mercenary team from the freighter. They threaten to kill Alex unless Ben surrenders. When the mercenaries kill the young girl in cold blood, Ben summons the smoke monster to take them out as well. In a flash forward, we see Ben visit Charles Widmore and threaten to kill his daughter, Penny. A little payback for what happened to Alex. Or maybe he'll get Sayid to do it. Sayid has been working for Ben as an assassin, which means he's another one of the Oceanic Six.