Stupidity: While Tommy and Snake Eyes are trying to escape the docks in the truck, the Yakuza men surround the truck and stab over a dozen swords in all parts of the cab. Not one of the men ever thinks to use their sword to slash the tires, allowing the heroes to make an easy escape.
Stupidity: The Arashikage clan has sworn to protect the jewel and placed it in a safe that can only be opened with the blood of the family. This presumes that no-one in the family will ever have a change of heart, which is actually shown happening with two members: Kenta and later Tommy when he uses the jewel in the climax. It also presumes that the Arashikage clan trusts that none of their family members will ever have illegitimate children until the end of time.
Stupidity: A lock which can be opened with your blood is horrible security. Leaving this as the only security measure on the safe, instead of also using a combination lock or other biometrics such as fingerprints, is done just so Snake Eyes has an easy way into the safe. A person's blood can be obtained through several means, most obviously by killing them, making this a completely unrealistic security measure.
