Chapter 12 is a bit story heavy, there is a great shoot out and another great car chase, but most of what is going on is pushing the story forward and, although it ends on a high note, its setting Vito up for a downward spiral.
Chapter 13 is a gun nut paradise. Before it gets hot and heavy Joe will ask if you want to visit Harry, and that's actually a great idea, you do want to be ready for the fight. Worth noting, at the end, I find it easier to shoot my way out and steal a convenient cop car for a fast get away, rather than trying to sneak away.
Chapter 14 finds Vito learning some hard truths about his family, his world, his friends, and mostly himself. This one keeps going, each time it seems like you're getting to the end another turn comes up and you have one more shootout and one more car chase. The first leg of the mission has a throwback to Mafia I, although its not a very heartwarming one.
Chapter 15 is the end of the line, old friends show up and make offers that can't be refused and culminate in a harrowing set of shootouts. The final showdown gives me trouble to this day, I've never been able to get a good handle on the mob movements. I'm not going to spoil the ending, there are lots of places where you can do that for yourself, but I will say, considering how heavily I had invested myself in this story, it is one of the most memorable game endings I've ever experienced.