Put the chicken breasts in a resealable plastic bag and add the chile powder, lime zest, 2 tablespoons of the olive oil and some salt and pepper. Seal the bag and shake to coat. Refrigerate for at least 30 minutes and up to 4 hours.
Heat a grill pan over medium-high heat. Remove the chicken from the bag and let any excess marinade drip off. Grill the chicken breasts until cooked through, 4 to 5 minutes per side. Keep warm.
Put the mango, kale, scallions, jalapeno and bell pepper in a large bowl. Whisk together the lime juice, chopped cilantro, 2 tablespoons of the reserved mango liquid, the remaining 1/4 cup olive oil and salt and pepper to taste in a small bowl. Pour half of it over the salad and toss to coat. Add more if you like.
Cut the chicken breasts into slices and fan them out. Pile the salad on a plate and arrange the chicken on top. (Or you can leave the breast whole and pile the salad on top of the chicken.)