Rinse the green beans, trim the ends, and cut them into 2-inch pieces.
Cook the chopped bacon in a Dutch oven over medium heat for 8 to 10 minutes until crispy. Set aside about a third for garnish, leaving the rest and 2 tbsp of fat in the pot.
Add the onion and cook 4 to 5 minutes until soft. Stir in the garlic and cook 30 seconds.
Stir in the brown sugar, smoked paprika, black pepper, and red pepper flakes for 1 minute.
Add the green beans and chicken broth. Bring to a boil.
Reduce the heat, cover, and simmer 20 to 25 minutes (10 minutes for canned beans) until tender.
Uncover and simmer 3 to 5 minutes to reduce the liquid. Stir in the butter and vinegar, then season with salt.
Top with the reserved bacon and serve hot.