A lot of this doesn't seem logical to me.
I keep reading that if you don't intend
to kill or harm, you don't reap any kamma from the action. What if for example, you are very tired but decide to drive anyway, fall asleep at the wheel and kill a person? You knew it was dangerous to drive, but you didn't intend to harm anyone, so you are in the clear? This may not be the best example, but there are many other possible examples of causing great harm to others without intending it, when we could have avoided it if we had been more thoughtful. What about shady business practices due to greed which result in people's life savings being lost, though you didn't intend harm to them, you knew the business practice was wrong?
yet on the other hand:
A tapeworm is infesting you and threatening your life, but you must not kill it? -- the kamma from that is so bad it would be better to let yourself die than kill the worm? And killing a worm intentionally is worse than killing a person through negligence?
What am I missing?