Here is the full list of all 13 Quests Unlimited achievements.
You've defeated 500 bosses!
You've drank 5000 potions!
You have completed 1000 quests!
You've defeated 50 bosses.
You've slain your first boss monster
You've drank 500 potions.
You've defeated 5000 monsters!
You have completed 100 quests.
You've defeated 500 monsters.
Completed 10 quests
A potion every now and again can't hurt
You've defeated 10 monsters
Just began your life as an adventurer.