The porpuse of achieving peace between organics and synthetics, find a solution, and the only one that really worked out was killing every apex civilizations out there in the galaxy, leaving only the younger ones alone. Why? Because the synthetics are always going to evolve more than the organics who then are going to see them as a threat (Quarians vs Geth), war is inevitable, and synthetics can wipe out every other organic life in the galaxy, advanced or not, they're stronger, smarter and fearless, so the Reapers are sort of the "Reboot" of the galaxy, they stop the conflict and then let new life arise again, it's an infinite cycle, a problem, and the solution to that is the extinction of those advanced species. The other one, by the Catalyst's view, is Synthesis, but he said that it's not something that can be forced by him, but an organic. Still, it's a forced peace, and a disgusting option IMO.