Here is the full list of all 35 Dead Island Riptide achievements. It takes around 40-50 hours to unlock all of the achievements on Windows.
Complete all the main quests cooperatively with any number of partners
Finish the game
Finish all quests in the game
Gain level 70
Find all collectibles
Find all pages from the guide book
Find all voice recordings of a journalist
Find all the secret files of Consortium
Find and kill all named champion monsters located in dead zones
Deafeat Harlow
Finish quests for Cecil in hospital
Enter the docks in Quarantine Zone
Make pact with Serpo
Survive the horde on the roof
Mark 100 opponents which then were killed by your coop partners
Gain access to a long range radio station
Find 50% of collectibles
Kill special enemies: Grenadier, Thug, Wrestler, Infected, Suicider, Screamer, Butcher, Floater.
Gain level 50
Clear out the cinema
Kill 10 zombies with one mine
Kill the Twins
Finish quests for Dr Kessler
Kill 100 enemies using charge attacks
Kill 100 zombies using boat speed boost
Reach Henderson
Successfuly defend the tunnels entrance
Install 5 barricades in any hub
Rescue 20 NPCs from clench
Kill 25 zombies with a chainsaw
Kill 100 zombies with thrown melee weapons
Kill 100 zombies with a kick.
Find a boat to travel through the jungle
Kill 50 zombies by smashing, decapitating or shooting them in the head
Escape from the ship