Finely chop half the chilli and thinly slice remaining chilli. Place finely chopped chilli in a bowl with garlic, lime rind, half the lime juice and half the oil. Stir to combine. Season with salt and pepper. Add octopus. Toss well to evenly coat. Cover. Refrigerate for 10 minutes.
Meanwhile, combine mango, avocado, onion, coriander and remaining lime juice and oil in a bowl. Season with salt and pepper. Set aside.
Preheat a barbecue or chargrill pan on medium-high heat. Cook octopus, in batches if necessary, turning, for 5 to 6 minutes or until charred all over and cooked through. Transfer to a board. Cut into bite-sized pieces.
Add octopus and spinach to mango mixture. Toss gently to combine. Serve salad, topped with sliced chilli, with lime wedges.
