I've posted this story on a different thread before I think but I'll post it here again.
There's an old Russian story called 'The Scorpion and the Frog'.
The story goes like this.
There once was a scorpion that wanted to cross a river and he asks a frog to give him a ride. But the frog was hesitant because he argued that the scorpion would sting him as they crossed. The scorpion argued that he would not sting him because they would both drown if he did so.
So the frog then agrees to give the scorpion a ride. But as they made it halfway across the river, the scorpion stung the frog.
As the frog begins to die the frog asks the scorpion why he did it and the scorpion replies, "I couldn't help it. It's in my nature."