According to Buddhism's concept of karma, is the intent often more important than the action?

The way I think about this is that there is at least 2 (if not more) consequences to every action (or "Karma", Karma itself literally means "action"). One consequence results from the impact the action has on the object it affects. The other results from the impact the action has on the subject performing the action itself. If I drive a car and inadvertently crush a worm without knowing it, the object is the worm and it got crushed. But my mind is unaffected, since I know nothing about it. On the other hand, if I get mad at somebody and plot to kill him, it affects my mind, but the person I'm plotting to kill is unaffected (assuming I just plot but did not proceed to kill him). Now, if I actually did kill him, then there is an impact on both the person being killed and on my mental state. In addition, I could also cause suffering to others, like the victim's children, for example. Think of Karma as actions and consequences. It can get a lot more complicated than that. Even a mental thought has consequences. Karma can be indirect and systemic. For example, by eating steak, I potentially contribute to causing my own high cholesterol, the suffering of the animal being eaten, affecting the environmental changes because of methane gas generated by the cow, impacting the land usage caused by growing corn to feed the cow, impacting the bacterial immunity caused by overused of antibiotics, etc. etc. Each of my action can affect me and everyone else, now and in the future! Which one is more important? To the worm, being crushed is more important. To me, plotting the killing, the fear, guilt, mental affliction is more important. To the person living 100 year from now, some other aspects of my action is more important. On top of that, Buddhism taught that everything is interdependent, interconnected, that the line between the Self and Others are not as clear cut as it appears. So the line is not just between "intent" and "non-intent". It's also related to the inter-dependence and inter-connectedness of everything. It's been said that the world cannot be at peace, unless I'm at peace, and vice versa. That's why the Buddha said the working of the Karma is one of the "http://imponderableshttp://en.wikipedia.org/wiki/Acinteyya", to complex to discuss. And that is why Buddhist spent a lifetime cultivating in order to develop the wisdom and serenity to stop causing Karma. That's what important!

If you are a hateful and spiteful person, you will succeed in living in a world of hate and spite, even if you are too incompetent to spread it to everybody else.  That's karma.