Slaycation Paradise

Living sex dolls are the enemies found on the second tour - New Amsterdam. Wait until you unlock the Perforator or Flamer ranged weapons(found blueprint and unlocked via Stash n Dash), which uses fire as it's main damage, and this achievement can easily be done in 1 tour( just don't fully summon the exit portal and hordes keep coming non stop).

Not 100% sure when the different weapons start showing up, but you will unlock the Perforator sooner than later. I'll update the guide in the future to be as accurate as possible.