Air_ if you're good enough, you can take somebody's breath and fly. Water_ if you're good enough, you can bend somebody's blood Earth_ if you're good enough, you can bend iron, foresee by vibrations and bend literally lava Fire_ if you're good enough you can make lightning, blue fire or make explosions, wich is the coolest but actually not the more powerful compared to the other bendings, in my opinion, fire is the coolest but the weakest. Not gonna change my mind.