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 overcaffeinated zombies fall in love
Two batteries 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
Flatten enemies with cars 10 times (friendly zombies do not count, must start the car yourself)
Complete a Gauntlet Level
Paint and sculpt 250 pieces of art
Two painted works of art fall in love
Completed the World 3 Finale
Paint Pictures for the Pirates
Two artists fall in love
Find Every Photograph
Completed the World 2 Finale
Two shy zombies fall in love
Complete a Pancake House Level
Two cone heads fall in love
Complete a Smorgasbord Level
Find a Secret Exit
Knock down every skull in Level 1-2
Completed the World 1 Finale
Complete a Trap Level
Complete a Camerabooth Level
Complete a Zoo Level
Find 10 Photographs
Find a Photograph
Beat a level with 3 Pancakes