Here is the full list of all 55 Ragnarok Clicker achievements. It takes around 200 hours to unlock all of the achievements on Windows.
Kill 1,500K monsters
Transcend the world 10 times
Kill 1,000K monsters
Beat Level 160
Beat Level 140
Kill 1,000 MVP Bosses
Transcend the world 5 times
Level up adventurers 10,000 times
Beat Level 120
Transcend the world 3 times
Click 10,000 times
Beat Level 100
Get 200 adventurer upgrades
Kill 100 MVP Bosses
Get 100 adventurer upgrades
Transcend the world 1 time
Kill 100K monsters
Level up adventurers 2,500 times
Beat Level 50
Kill 10 MVP Bosses
Get 50 adventurer upgrades
Level up adventurers 500 times
Get 25 adventurer upgrades
Beat Level 25
Level up adventurers 100 times
Kill 1,000 monsters
Kill 10,000 monsters
Beat Level 10
Kill 100 monsters
Click 1,000 times
Beat Level 1,200
Beat Level 1,400
Beat Level 1,600
Beat Level 1,800
Beat Level 2,000
Beat Level 2,200
Beat Level 2,400
Beat Level 2,600
Beat Level 2,800
Beat Level 3,000
Beat Level 3,200
Beat Level 3,400
Beat Level 3,600
Kill 10,000 MVP Bosses
Kill 100K MVP Bosses
Click 50,000 times
Click 100K times
Click 250K times
Level up adventurers 25,000 times
Level up adventurers 50,000 times
Open 10,000 Chests
Transcend the world 25 times
Transcend the world 50 times
Transcend the world 100 times
Transcend the world 250 times