Damaging isnt the way to go. A feathweight weapon would need all day to do enough damage to knock out a heavy, and battery life aside that wouldnt work. Well, maybe against a poor heavyweight, but not Tornado.

I think borrowing an idea from Alexs Ramthrax would work here. Make a 10 KG wedge robot with powerful drive, similar to the first Micro Mute, but make it a cluster bot and attach an ant-weight to the back. Drive the wedge under Tornado to beach it, then release the ant-weight. Tornado immobolised, and the ant runs free allowing the feathweight to win on a technicality