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