Here is the full list of all 15 Biglands: A Game Made By Kids achievements.
Beat Lava Land
Beat Cloud Island
Beat Mars
Beat Twilight Forest
Beat Dr. Evil Herobrine's Lab
Beat the Graveyard
Beat Humanya Ka,olana
Beat the Game
Fully Upgrade Any Weapon
Fully Upgrade All Weapons
Die 300 times
Jump 10000 times
Attack 10000 times
Kill 2000 monsters
Collect 7000 items