I wouldn't say humans are the most powerful animal on the planet, with equal playing field we can easily be bested by many animals. Our ability to use tools is all that makes us superior, imagine a Polar bear with body armor and a large caliber machine gun. I get what your saying tho.
Spider bites always make me think of a boss at my company, I really don't like the guy nor does anyone else. He had a big welt on his forehead for a week and he claimed it was a spider bite but in reality he had been jumped by a guy who found out he was boffing his wife.
The smallest creatures are often the most deadly, spiders are definitely on that list, but think of viruses, they are microscopic and can really tear you up or even kill you. Size does not always relate to power. It very humbling to think something so tiny can do so much damage.