Here is the full list of all 21 KingAndSlaves achievements.
Complete the village head checkpoint
Complete Viscount Dolon
Complete the mercenary leader checkpoint
Complete the Wolf Gate
Complete General Gate
Complete the assassination of the leader
Complete the Master Devil Level
Complete the Frost King Gate
Complete the Ancient God Ontology Gate
Complete and see through life
Killed by a debt collector
Barracks up to full grade
99 lashes
Equipment sold 2000
Slaves sold 99
300 village looting
Ninety-nine children
Having acquired all occupations
The arena won 30 times