I don't think there's a KOM 'achievement'.

The KOM jersey is worn by the person who has the fastest climbing time for the 'KOM segment'. You can also be awarded the KOM jersey, say, if you're second on the 'leaderboard' and the leader leaves the program (and you 'inherit' the KOM jersey).

Same idea applies for the Sprinter's (green) jersey and the overall lap time (orange) jersey.