In a large Dutch oven or pan over medium heat, brown the bacon. When the bacon is about halfway browned add the chopped onion. Cook until the bacon is browned and the onion is soft. Add the garlic and cook for 1 minute, stirring constantly.
Add the collard greens and cook until wilted and slightly softened. Add the chicken broth, apple cider vinegar, sugar, Cajun seasoning, paprika, and crushed red pepper. Cover and simmer for 45-60 minutes, letting the liquid cook down and the greens really soften. Drain most of the liquid or use a slotted spoon to remove it. Salt and pepper to taste. For best results, serve promptly.