Here is the full list of all 35 Dead Island: Riptide Definitive Edition achievements worth 1,000 gamerscore.
Obtain level 50
Find 50% of collectibles
Finish the game
Defeat Harlow
Enter the docks in Quarantine Zone
Make pact with Serpo
Survive the horde on the roof
Gain access to a long-range radio station
Clear out the cinema
Reach Henderson
Rescue 20 NPCs that have been grabbed by monsters
Kill special enemies: Grenadier, Thug, Wrestler, Infected, Suicider, Screamer, Butcher, Floater.
Successfully defend the tunnel entrance
Kill 50 monsters by smashing, decapitating or shooting them in the head
Find a boat for use in the jungle
Escape from the ship
Finish all quests in the game
Find all the secret files
Obtain level 70
Install a total of 5 barricades during hub defense
Complete all the main quests cooperatively with any number of partners
Find all collectibles
Find all pages from the guide book
Kill the Twins
Find all the volunteer's voice recordings
Kill 10 monsters with one mine
Kill 100 monsters with thrown melee weapons
Kill 100 monsters with a kick
Kill 100 monsters using the boat's speed boost
Kill 100 enemies using charge attacks
Kill 25 monsters with a chainsaw
Finish quests for Dr. Kessler
Finish hospital quests for Cecil
Mark 100 opponents which were then killed by your co-op partners
Find and kill all the most dangerous monstrosities located in dead zones