Here is the full list of all 13 Kingdom of EXPLORERS achievements.
Upgrade Sworld to Lv. 5 for both players.
5 Dark Knight Dead.
Upgrade Shield to Lv. 5 for both players.
Upgrade Axe to Lv. 5 for both players.
Upgrade Pickaxe to Lv. 5 for both players.
Defeat the Hard Rock boss.
Defeat your first Dark Knight.
Defeat the Pharaoh of Lava boss.
Defeat the Fiery Cyborg boss.
Defeat the Lapidated Skeleton boss.
Defeat the Verdant Beast boss.
Defeat the Orc Commander boss.
Defeat the Dark Lord boss.