This may be missing the point, but when talking about a population of 600 people, “This intervention will save 200 lives” and “This intervention will result in 400 deaths” actually mean different things. The former means that the number of deaths will be decreased by 200 if you do the intervention, whereas the latter means that the number of deaths will be increased by 400 if you do the intervention. Relative to not doing the intervention. I realize you meant it to be “relative to everyone dying” and “relative to no one dying”, respectively, but that is not what the sentences mean in English if you interpret them naturally.
This may be missing the point, but when talking about a population of 600 people, “This intervention will save 200 lives” and “This intervention will result in 400 deaths” actually mean different things. The former means that the number of deaths will be decreased by 200 if you do the intervention, whereas the latter means that the number of deaths will be increased by 400 if you do the intervention. Relative to not doing the intervention. I realize you meant it to be “relative to everyone dying” and “relative to no one dying”, respectively, but that is not what the sentences mean in English if you interpret them naturally.