Here is the full list of all 7 Harem King: Peasant to Princess Gotta Breed 'Em All! achievements.
Start your harem
Add the citizens of the kingdom to your harem
Add the Elves to your harem
Add the Demi-humans to your harem
Begin your daily life as the Harem King
Add the biggest threats to the kingdom to your harem
Go even further beyond, adding girls from other worlds to your harem!