Here is the full list of all 28 Lovers in a Dangerous Spacetime achievements worth 1,000 gamerscore.
Pirouette 15 times in a single level.
Defeat Ursa Major without taking a punch.
Use three different types of Yamato weapons in a boss fight.
Defeat King Cepheus.
Finish a level without crossing paths with your partner.
Escape a white dwarf without shooting or ramming it.
Have 20 cells at one time on the Metal-Beam shield.
Defeat Orion.
Fill up all gem slots in a fully upgraded ship.
Kill 20 enemies with security guns in a single level.
Defeat Cetus.
Finish a level after removing all fog of war.
Make two Power-Metal missiles collide.
Throw a gem into a station that is being used by another player.
Defeat Ursa Major.
Beat any level in two player mode.
Finish the tutorial.
Use every station in a single level.
Beat any level with the help of your trusty space-pet.
Finish a level without taking damage.
Play through a campaign without using any gems.
Earn one of each type of ship badge.
Rescue every captured friend.
Defeat Cetus while its head is underwater.
Deliver the final blow to Orion using a solar flare.
Remove all of King Cepheus's shields.
Have 10 unused gems in your ship at one time.
Survive after being fully enveloped by a bomb trap.