Here is the full list of all 6 VR Guardians achievements.
Successfully defeated the Lava World boss, Fire Guardian - IGFRIT.
Successfully defeated the Underwater World boss, Water Guardian - LHYR.
Slashed the SKULL to awaken the Fire Guardian - IGFRIT.
Successfully entered the Lava World
Slashed the ICE ROCK to awaken the Water Guardian - LHYR.
Successfully entered the Underwater World