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