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