3. Signs Aliens (Water)
The aliens from Signs are arguably the stupidest villains from any movie ever. They opted to invade Earth and fight a ground war without any ranged weaponry or any technology of any kind, which was stupid enough, but to invade a planet whose surface area is 70% water when their weakness was water was just unforgivable. Signs gives the message to never lose faith because everything has a meaning and it becomes apparent that the reason that the lead character's daughter, Bo, has been leaving glasses of water around the house for so long is because one of the aliens was to come in the house, and using the glasses of water to cover it in water was one of the decisive factors in defeating it.