Cook bacon in a large saucepan or small stockpot over medium heat, stirring occasionally, until crisp, 8 - 10 min., then transfer bacon to a paper towel-lined plate; set aside.
Add onion to bacon fat and cook 2 min., stirring occasionally. Increase heat to medium-high and add pork. Cook 6 - 8 min., stirring occasionally, until onions are crisp-tender. Stir in chili powder, paprika, tomatoes and their juices, and water. Bring to boil, reduce to a simmer and cook 35 - 45 min., stirring occasionally, until pork is tender.
Stir in beans and 2/3 of the bacon. Cook 10 min until heated through, stirring occasionally. Salt to taste. Serve garnished with remaining bacon, sour cream and scallions.