The man-made object responsible for the most deaths worldwide is the tobacco cigarette. It isn't even close.
Tobacco kills 443,000 Americans a year and 5 million people a year worldwide. This is more than the total number of people killed by cars and firearms combined. Cars kill about 32,000 Americans each year and 1.3 million people worldwide, while firearms kill about 32,000 Americans each year and "several hundred thousand" people worldwide.
100 million people were killed by tobacco in the 20th century. This is more than the death toll from World War 1 (17 million) and World War 2 (50 to 70 million) combined.
From a strictly utilitarian perspective, would there be anything to be gained by, say, starting a campaign of assassination against executives of tobacco companies?
Would destruction of tobacco crops or processing facilities be more effective? Eliminating a few executives won't slow distribution significantly, unless their positions are already held by the ablest people and their replacements would be less able to distribute the product.
Targeting executives may win them sympathy. I think sales would go up, as the news reports would serve much the same role as advertising.