This battle takes place on top of an incomplete skyscraper. Beetle has three different attacks: His laser blasts (used for far range), laser sword (used for close range) and his shield (used as a counter against combos). Laser blasts are simply spheres of energy that Beetle will use when he's in mid-air. This is probably his most-used attack. The shield is probably the most-damaging attack. When you're punching and kicking Beetle, he'll try to use an attack to push you away. It's a large shield that extends quite far and seems to be made up of the same energy Beetle uses for his blasts. Get caught in this and there's no way out until it ends.
First thing, switch your special to adrenaline (Nintendo DS version). Now he should start off blasting at you with his multi-directional lasers flying in the air. You can't dodge these blasts so don't try. All you have to do to avoid these is run back and forth under him. Whenever you see an opportunity, jump up and start beating him with air combos. If your Spider Sense goes off while doing this simply jump away to avoid his Shield move. Repeat this until he starts getting close to the ground. At this point you should jump over his beams until you're up close enough to punch him. do this three times in a row and then move away from him. Then use the adrenaline rush whenever you can and he should be taken down fairly easily.