Achievements
Complete each achievement to get the allotted gamerscore.

Unlockable How to Unlock
Grime Buster (10) Clean up after Fred and George at The Burrow
Used the Pensieve (10) View Dumbledore's first memory of Tom Riddle in the Pensieve
Quidditch Captain (10) Assemble the Gryffindor Quidditch Team
Great Party (10) Create a great Christmas party for Slughorn
Good Deed (20) Help the student retrieve her stolen Gobstone
Great Mate (20) Help Ron avoid Lavender
Hidden the Book (20) Hide the Half-Blood Prince's Potions Book
Portrait Novice (10) Use your first portrait shortcut
Portrait Pro (20) Use all of the portrait shortcuts
Adventure completed (100) Conclude the adventure
Crest Collector 1 (10) Complete Crest Collector Level 1
Crest Collector 2 (10) Complete Crest Collector Level 2
Crest Collector 3 (10) Complete Crest Collector Level 3
Crest Collector 4 (10) Complete Crest Collector Level 4
Crest Collector 5 (20) Complete Crest Collector Level 5
Crest Collector 6 (20) Complete Crest Collector Level 6
Crest Collector 7 (20) Complete Crest Collector Level 7
Crest Collector 8 (20) Complete Crest Collector Level 8
Crest Collector 9 (30) Complete Crest Collector Level 9
Crest Collector 10 (30) Complete Crest Collector Level 10
Crest Collector 11 (30) Complete Crest Collector Level 11
Crest Collector 12 (40) Complete Crest Collector Level 12
Crest Collector 13 (50) Complete Crest Collector Level 13
Crest Collector 14 (60) Complete Crest Collector Level 14
Potions Beginner (10) Earn the Potions Beginner's Luck Badge
Speedy Brewer Badge (10) Earn the Speedy Brewer Badge
Potions Club Star (10) Earn the Potions Club Star Badge
Potions Club Veteran (20) Earn the Potions Club Veteran Badge
Master Potioneer (50) Earn the Master Potioneer Badge
Duelling Beginner (10) Earn the Duelling Beginner's Luck Badge
Reflex Badge (10) Earn the Reflex Badge
Duelling Champion (10) Earn the Duelling Club Champion Badge
Duelling Veteran (20) Earn the Duelling Veteran Badge
Master Duellist Badge (50) Earn the Master Duellist Badge
Quidditch Beginner (10) Earn the Quidditch Beginner's Luck Badge
Precision Flyer Badge (10) Earn the Precision Flyer Badge
Combo Flyer Badge (10) Earn the Combo Flyer Badge
Keen Flyer Badge (20) Earn the Keen Flyer Badge
Master of Flying (50) Earn the Master of Flying Badge
Burrow Defender (20) Successfully protected The Burrow
Mystery Solved (20) Retrieved Slughorn's missing memory
Quidditch Champion (30) Won the Quidditch Cup
Escaped the Cave (40) Escaped the Cave
Hogwarts Crest Unlockables

Collecting so many crests around Hogwarts will unlock certain single and multi player things.

Unlockable How to Unlock
3 Hogwarts Crests Two Player Dueling Pack 1: Draco & Luna
8 Hogwarts Crests More health in duels
14 Hogwarts Crests Two Player Dueling Pack 2: Training Ground Dueling Arena
21 Hogwarts Crests Dungbombs in prank boxes around Hogwarts
29 Hogwarts Crests Two Player Dueling Pack 2: Crabbe & Goyle
38 Hogwarts Crests Score boost in flying events
48 Hogwarts Crests Exploding Cauldrons in prank boxes around Hogwarts
59 Hogwarts Crests Two Player Dueling Pack 4: The Transfiguration Dueling Arena
71 Hogwarts Crests Even More health in duels
84 Hogwarts Crests Two Player Dueling Pack 5: Ginny & Hermione
98 Hogwarts Crests Love Potion in Potions Club
113 Hogwarts Crests Two Player Dueling Pack 4: Paved Courtyard Dueling Arena
129 Hogwarts Crests More mini-crests with each cast