Here is the full list of all 35 Love is Dead achievements.
Find Your Pets
Collect 213 Pancakes
Completed the World 7 Finale
Two star zombies fall in love
Completed the World 6 Finale
Zombify the Mad Scientist
Two batteries fall in love
Two overcaffeinated zombies fall in love
Free a human from stasis
Completed the World 5 Finale
Zombify every Spearhuman and Bowhuman in Level 5-5 (they MUST be eaten, they cannot blow up unless they've already been eaten)
Completed the World 4 Finale
Blow up 6 Pirate Lackeys with your own cannonballs
Paint Pictures for the Pirates
Completed the World 3 Finale
Paint and sculpt 250 pieces of art
Complete a Gauntlet Level
Two artists fall in love
Two painted works of art fall in love
Two shy zombies fall in love
Two cone heads fall in love
Flatten enemies with cars 10 times (friendly zombies do not count, must start the car yourself)
Find 10 Photographs
Find Every Photograph
Completed the World 2 Finale
Complete a Pancake House Level
Complete a Smorgasbord Level
Completed the World 1 Finale
Complete a Trap Level
Complete a Camerabooth Level
Complete a Zoo Level
Find a Secret Exit
Knock down every skull in Level 1-2
Find a Photograph
Beat a level with 3 Pancakes