Here is the full list of all 24 Sylvio 2 achievements.
You finished the game.
NEW_ACHIEVEMENT_DESC_1_23
You found all devil sculptures.
You found all words in the static and recordings in location 9.
You've found more than 185 hidden messages by analyzing.
You found all words in the static and recordings in location 8.
You found all the words in the static.
You found all words in the static and recordings in location 7.
You've found more than 150 hidden messages by analyzing.
You found all words in the static and recordings in location 6.
You visited all the islands.
You found a body.
You found all words in the static and recordings in location 5.
You've found more than 100 hidden messages by analyzing.
You found all words in the static and recordings in location 4.
You found all words in the static and recordings in location 3.
You found all words in the static and recordings in location 2.
You've found more than 30 hidden messages by analyzing.
You found all words in the static and recordings in location 1.
You've found more than 5 hidden messages by analyzing.