Brotato

These achievements are all cumulative, and despite sounding like a huge amount of enemies, especially for this achievement, these achievements will all unlock relatively early in your time with this completion. To put it in perspective, I unlocked Survivor 3 (3G) for killing 5000 enemies during my very first run, Survivor 4 (4G) at the very start of my third run, and this achievement a few runs later. Considering you need to do 44 successful runs (once with each character) for the completion, these achievements will come naturally.