Slice the stems from the collard greens, halve the leaves lengthwise and layer them in stacks of 6 or 7. Roll the leaves tightly from the short end, and slice them into ribbons about 1/4-inch wide.
Add the collards to the boiling water and cook until wilted and tender, 2 to 3 minutes. Drain thoroughly and set aside. Refill the pan with salted water and bring to a boil again for the spaghetti.
Fry the bacon in a large pan until crisp, transfer to a paper towel-lined plate and drain all but 1 tablespoon of the fat from the pan.
Add the olive oil to the bacon fat and heat over medium heat. Add the garlic and sauté until fragrant, 1 minute. Add the onion and continue cooking until soft and translucent, 2 to 3 minutes longer. Add the vinegar, chicken broth and apples, combine well, then add the collards and toss together with tongs. Season to taste with salt and pepper.
Cook the spaghetti according to package directions, drain and add to the collard mixture. Add the bacon and pecans and toss to combine.
Plate individual servings and top with freshly ground black pepper. Serve immediately.