No, you don't understand Bitcoin at all. Sure they can kill you, so what? They get nothing. And guess what, there are also ways to hide the information necessary for heirs to receive the bitcoins in the event of your death at a future date. I won't even get into the ways bitcoins can be used for anonymous vigilantism in the event of a death by foul play.
None of what you said is unique to bitcoin.Rich and powerful people had been doing these for centuries.
The rich and powerful usually resort to violence to achieve their ends. Bitcoin makes it trustless and non-violent to level the playing field. Their wealth will no longer be maintained by force, it will need to be earned through honesty and empathy.