Achieving 100% completion in Terraria involves completing various tasks ranging from simple actions like gathering materials to complex challenges like defeating bosses under specific conditions. Here’s a guide on how to unlock all achievements in Terraria, categorized by the type of activity you need to engage in.

General Gameplay Achievements

1. Timber!! — Chop down your first tree.
2. No Hobo — Build a house suitable enough for your first NPC, the Guide, to move into.
3. Stop! Hammer Time! — Obtain your first hammer via crafting or otherwise.
4. Ooo! Shiny! — Mine your first nugget of ore with a pickaxe.
5. Heart Breaker — Discover and smash your first heart crystal underground.
6. Heavy Metal — Obtain an anvil made from iron or lead.
7. I Am Loot! — Discover your first large underground chest.
8. Star Power — Increase your mana capacity by picking up a fallen star.
9. Hold on Tight! — Equip your first grappling hook.
10. Eye on You — Defeat the Eye of Cthulhu, an early boss in the game.
11. Smashing, Poppet! — Break a Shadow Orb or Crimson Heart in the Corruption or Crimson.
12. Worm Fodder — Defeat the Eater of Worlds or Brain of Cthulhu, significant bosses in Corruption or Crimson.
13. Mastermind — Defeat the Brain of Cthulhu, a boss in the Crimson biome.
14. Worm Scarf — Defeat the Eater of Worlds, a boss that can be found in the Corruption biome.

Crafting and Collection Achievements

1. Crafty — Use every crafting station at least once.
2. All in the Family — Have every possible NPC move into your town.
3. Matching Attire — Equip armor in all three armor slots: head, chest, and feet.
4. Fashion Statement — Equip armor or vanity clothing in all possible slots.
5. Dye Hard — Equip a dye in every possible dye slot.

Exploration and Combat Achievements

1. Rock Bottom — Reach the bottom of the World.
2. Into Orbit — Reach space, above the World.
3. Lucky Break — Survive a long fall with just a sliver of health remaining.
4. It’s Hard! — Unleash Hardmode by defeating the Wall of Flesh.
5. Begone, Evil! — Smash a Demon or Crimson Altar with a Pwnhammer.
6. Extra Shiny! — Mine a powerful and rare ore like Adamantite or Titanium.
7. Pet Hoarder — Find all the pets.
8. Achievement — Kill a Nymph, a rare and elusive enemy.
9. Head in the Clouds — Equip a pair of wings.

Boss Achievements

1. Wall of Flesh — Defeat the Wall of Flesh, the boss that unleashes Hardmode.
2. The Frequent Flyer — Spend over 1 hour airborne with wings or rocket boots.
3. Baleful Harvest — Defeat the Pumpking during a Pumpkin Moon event.
4. Ice Scream — Defeat the Frost Legion.
5. Tin-Foil Hatter — Defeat the Martian Madness event.
6. There are Some Who Call Him — Kill Tim, a special undead wizard.
7. Big Booty — Unlock one of each type of large treasure chest.
8. Fish Out of Water — Defeat Duke Fishron, a hardmode boss summoned in the Ocean.
9. Obsessive Devotion — Defeat the Moon Lord, the final boss of Terraria.

Event and Special Achievements

1. Do You Want to Slay a Snowman? — Triumph over the Frost Moon.
2. Gelatin World Tour — Defeat every type of slime there is.
3. Real Estate Agent — Have all possible room NPCs living in your world.
4. Prismancer — Obtain a Rainbow Rod.
5. Rainbows and Unicorns — Fire a rainbow gun while riding on a unicorn.

Completing all these achievements requires a balanced approach to all aspects of Terraria gameplay, including exploration, combat, crafting, and community building. It will take time, patience, and a strategic plan to fully master Terraria’s diverse world.