The heartwarming ending: Hawk ruins his son's life
So, the kid was in an elite military school, being cared for by his wealthy grandfather - who is portrayed as the villain by trying to take care of the boy. Everything the grandfather did were with his grandson's best interests at heart, trying to save him from Hawk - the guy who abandoned the kid. Now let's see: Hawk sticks his son behind the wheel of a fully-loaded big rig and let's him drive for the first time in his life on a state highway, so they can bond over a bit of reckless endangerment; when told he's not allowed on the grandfather's property to see the kid, he rams through the house in a semi...which easily could've killed the boy and anyone else in the way, it was pure luck the kid wasn't near the front door - the kid even straight up tells Hawk he feels safer and more secure with his grandfather; so that ending with Hawk and son trucking off into the sunset together is actually depressing as hell when you realize not only is the kid now in custody of the guy who abandoned him and repeatedly endangered his life, that security in his future the grandfather was trying to provide is gone now.
Seriously, there was nothing happy about the way that ended. Hilarious, but not happy at all