Here is the full list of all 74 King of Crabs achievements.
Unlock all Common Crabs
Unlock all Rare Crabs
Unlock all Super Rare Crabs
Unlock all Mega Rare Crabs
Unlock all Legendary Crabs
Become King
Become Mega Big
Reach Rank Crab Lord
Reach Rank Crab Master
Reach Rank Crab Champion
Reach Rank Crab King
Reach Rank Crab Emporer
Reach Rank Crab Legend
Reach Rank Crab God
Perform a Normal Streak
Perform a Mega Streak
Perform a Rampage Streak
Perform 10 Revenge Kills
Buddy Up with 10 players
Score 250,000 Points
Score 500,000 Points
Score 1,000,000 Points
Score 2,000,000 Points
Score 4,000,000 Points
Complete 10 Quests
Complete 50 Quests
Complete 100 Quests
Complete 200 Quests
Unlock the Brown Crab
Unlock the Rainbow Crab
Unlock the Blue Crab
Unlock the Mitten Crab
Unlock the Spanner Crab
Unlock the Elbow Crab
Unlock the Stone Crab
Unlock the Candy Crab
Unlock the Hermit Crab
Unlock the Giant Mud Crab
Unlock the Snow Crab
Unlock the Yeti Crab
Unlock the Lobster
Unlock the Tasmanian Crab
Unlock the Coconut Crab
Unlock the Mantis Crab
Unlock the Alien Crab
Unlock the Robot Crab
Unlock the Demon Crab
Reach Level 50 with Brown Crab
Reach Level 50 with Rainbow Crab
Reach Level 50 with Blue Crab
Reach Level 50 with Mitten Crab
Reach Level 50 with Spanner Crab
Reach Level 50 with Elbow Crab
Reach Level 50 with Stone Crab
Reach Level 50 with Candy Crab
Reach Level 50 with Hermit Crab
Reach Level 50 with GiantMud Crab
Reach Level 50 with Snow Crab
Reach Level 50 with Yeti Crab
Reach Level 50 with Lobster Crab
Reach Level 50 with TasmanianGiant Crab
Reach Level 50 with Coconut Crab
Reach Level 50 with MantisShrimp Crab
Reach Level 50 with Alien Crab
Reach Level 50 with Robot Crab
Reach Level 50 with Demon Crab
Unlock the Ghost Crab
Reach Level 50 with Ghost Crab
Reach Level 50 with Vampire Crab
Unlock the Vampire Crab
Reach Level 50 with Dino Crab
Unlock the Dino Crab
Unlock the Octo Crab
Reach Level 50 with Octo Crab