Deaths directly caused by him: 1,800 to 3,200 in program of drone assassinations.
Total number of lives saved by him: Hundreds of thousands at least.
National healthcare system may save as many as 30,000 lives a year. The number depend on how much more efforts to sabotage it there are or if the system is replaced by a better one.
Endind the Second Iraq War saved a minimum of 36,000 (UN estimate for war death in 2006) to as many as 100,000 Iraqis (Opinion Research Business study estimate) for every additional year of war that another president like McCain or Palin would have done.
Ending the Afghanistan War saved an unknown number. Since there are few accurate figures kept on Afghan civilian deaths, it is hard to know. For both wars, Obama deserves only partial credit for ending, with more credit due to Afghan, Iraqi, and US public opposition.
Ending chemical warfare in Colombia, the spraying of glyphosate designed to eradicate coca, saved an unknown number of Colombian and Ecuadoran lives.
Arms control agreements reducing nuclear weapons by two thirds.
Partly responsible for ending Syrian biochemical weapons program.
Partly ending racist drug sentencing.
Presidents Body Counts: The Twelve Worst and Four Best American Presidents Based on How Many Lived or Died Because of Their Actions