Ozark's biggest question, proposed by the show in its pilot episode back in 2017, has finally been answered by the series finale at the end of season 4.  

the seemingly never-ending chaos and turmoil concocted by the Byrde family has been laid to rest at last.  

As each season of the show has come and gone, the level of danger has increased and pushed the Byrdes beyond their breaking point 

Never before on television has there been a family better adapted to overcoming obstacles than the Byrdes, with parents Marty and Wendy acting as the focal point of said adversity.  

Their ability to maintain reason over retaliation knows no bounds. They are by no means the perfect and happy family they promote themselves as 

but they refuse to buckle under immense pressure. Whether the danger is externally caused or more often than not internally caused 

After they've united at last as a family in spirit and in flesh, Mel returns to haunt the Byrdes and confronts Marty and Wendy about Ben's death. 

Mel's obsessive nature over Ben's disappearance despite Ben having saved the Byrdes provides a stumbling block for Marty and Wendy throughout Ozark season 4