I used to watch Naruto a long time ago and I remember there being a filler anime about people using lightning techniques..
One thing I remember specifically was that one of the ninjas was using a lightning weapon that was supposed to be able to cut through anything including Chakra...
The problem was that one of the Ninjas from Hidden Leaf if I remember correctly was fighting them and stopping the blade with a regular Kunai...
How does that work? If the lightning weapon can cut through anything including Chakra why would a regular kunai stop it?
After a quick research the weapon is the Sword of the Thunder God... as stated on Naruto Wikia: Sword of the Thunder God - Narutopedia, the Naruto Encyclopedia Wiki
As shown in Aoi's fight with Naruto Uzumaki and Sasuke Uchiha, the blade was shown to not only be able to easily cut through any solid object, but also through chakra-based substances as well.
After rewatching the episodes again the person using the sword swung at a ninja then a couple of kunais is seen to drop to the floor blocking the attack...
The Kunais are seen to be intact... So if this sword can cut through anything why was his attack stopped by them?