I've always kinda wondered whether Plate Armor would serve as a Farraday Cage of sorts, or a lightning rod, such that current actually would NOT flow through the wearer, but go straight to the ground or just move to the outside of the armor. I don't hold much stock in this hypothesis, but I'm just wondering.
OT: Pretty much any armed aircraft/starcraft would serve. Just take off, and what options do they have? Maybe longbows or slings, but I think armor plating, miniguns, missiles, laser cannons, ion bombs etc. would probably win, even at 15,000 to 1. I think even a dreadnaught or tank could be taken down by 15,000, unless you stay out of range, which is the key. Swords in treads, jamming up motors or joints, there's a lot of little things that when repeated hundreds of times would probably disable your machine and end with you killed. Provided the knights are devoted enough to killing you after seeing you massacre several thousand of them.