Heat remaining 2 tablespoons oil in a skillet over medium heat. Add garlic and sauté for 30 seconds, making sure it does not burn. Stir in tomatoes; cook, stirring often, until heated through, about 1 minute. Add broth and beans; bring to a simmer. Add spinach or kale in batches, and cook, tossing gently, until greens are wilted after each addition. Stir in lemon juice, olives, remaining ½ teaspoon of salt and ¼ teaspoon of black pepper, and red pepper flakes (if using). Nestle fish back into the bean mixture, garnish with fresh parsley, and drizzle with a little extra olive oil (if desired). Serve immediately. Enjoy!