The gas ganisters would be too heavy. A better payload is razor blades / needles coated in some potent venom poison, like tetrodotoxin ricin or cone snail toxin

The gas ganisters would be too heavy. A better payload is razor blades / needles coated in some potent venom poison, like tetrodotoxin ricin or cone snail toxins. Launch 1000 of these drones and you can kill an army in no time.