Looks like a real fighter one that is used in betta fights. These guys might know more then you know about the fish. He could be from campion fighting lines and if so he could make his owner a lot of money if fought and then bred. Most fighter are not all black. That's my only guess or it's a crazy scram.
I don't know much about the fish fighting world but for example a racking grey hound is going to be a hell of a lot more money when in his prime then a pet greyhound. Because there is money to be made on him. But as soon as he can no longer run as fast the poor dog is not worth anything. Much like these fighting bettas.