We know from the Death Star Technical Companion that the number of people aboard the first Death Star (including troopers, gunners, crew, pilots, staff, etc.) was 1,179,293. That's how many people Luke killed in a single Force-inspired instant. Then you add all the other people he's killed in his adventures (though as a friend of mine has said, that's essentially a rounding error in the death toll).
How does that compare to the number of people directly killed by Darth Vader (including the sand people, even if he was technically still Anakin then) over his lifespan, off-screen or on?