Street Fighter 4 - Unlock Akuma

Unlock Gouken:
First, unlock Akuma, Sakura, Dan, Cammy, Fei Long, Gen and Rose then Fight him on arcade mode. Get at least 2 perfects and 2 Ultra Finishes to unlock him.

Unlock Cammy:
End the arcade mode with Crimson Viper

Unlock Dan:
End the arcade mode with Sakura

Unlock Fei Long:
End the arcade mode with Abel

Unlock Gen:
End the arcade mode with Chun-Li

Unlock Rose:
End the arcade mode with M.Bison

Unlock Sakura:
End the arcade mode with Ryu

Unlock Seth:
End the game with all the other characters

Achievements:

Bronze:

All Dolled Up
Objective: Set your Title and Icon.

Arcade Rat
Objective: Clear Arcade Mode with 1 character on Medium or higher difficulty.

Challenge Expert
Objective: Clear all Challenges in Challenge Mode.

Challenger
Objective: Clear a Challenge in Challenge Mode.

Color Guard
Objective: Unlock all Colors.

Crowd Pleasing Master
Objective: Perform 10 Personal Actions.

EX-cellent Master
Objective: Perform 100 EX Special Moves.

First Victory
Objective: Win 1 ranked match.

Focus Master
Objective: Perform 100 successful Focus Attacks.

Hard Fought Battles
Objective: Play 200 online battles. ranked match or player match

Last Man Standing
Objective: Cleared HARD Survival in Challenge Mode.

Lobbyist
Objective: Create 10 multiplayer lobbies.

Medal Collector
Objective: Collect 100 Medals.

Medal Hunter
Objective: Collect 500 Medals.

Medal Master
Objective: Collect 1,000 Medals.

Medals Get
Objective: Collect all Medal types.

No Challenge Too Hard
Objective: Cleared HARD Trial in Challenge Mode.

No Sweat
Objective: Unlock all Personal Actions.

Proof of Battle
Objective: Play 500 online battles. ranked match or player match

Rapid Fighter
Objective: Clear NORMAL Time Attack in Challenge Mode.

Simply Perfect
Objective: Achieve 10 Perfect victories.

Special Move Master
Objective: Perform 100 Special Moves.

Speed King
Objective: Cleared HARD Time Attack in Challenge Mode.

Super Combo Champion
Objective: Perform 50 Super Combo finishes.

Super Combo Master
Objective: Perform 100 Super Combos.

Taking On All Comers
Objective: Fight 10 opponents via fight requests.

Technical Fighter
Objective: Clear NORMAL Trial in Challenge Mode.

The Journey Begins
Objective: Win 10 online battles. ranked match or player match

The Line Starts Here
Objective: Win 3 ranked matches in a row.

The Road to Battle
Objective: Play 100 online battles. ranked match or player match

The World Warrior
Objective: Unlock all characters.

Tough Cookie
Objective: Clear NORMAL Survival in Challenge Mode.

Ultra Combo Champion
Objective: Perform 50 Ultra Combo finishes.

Ultra Combo Master
Objective: Perform 100 Ultra Combos.

Way of the Fist
Objective: Win 5 online battles. ranked match or player match

Silver:

10 Years Too Early
Objective: Win 50 online battles. ranked match or player match

I Got Next
Objective: Win 5 ranked matches in a row.

Icon Master
Objective: Collect all Icons.

Legendary Champion
Objective: Defeat Gouken and clear Arcade Mode in Hardest difficulty.

Playing To Win
Objective: Win 10 ranked matches in a row.

Save Your Quarters
Objective: Clear Arcade Mode without using a single continue on Medium or higher difficulty.

Storied Reputation
Objective: Clear Arcade Mode with all characters on Medium or higher difficulty.

Sunny Daze
Objective: Perform 365 flashy background finishes.

Title Master
Objective: Collect all Titles.

World Champion
Objective: Clear Arcade Mode on Hardestb difficulty.

Gold:

10 Years Too Late
Objective: Win 100 online battles. ranked match or player match

The Gold Standard
Objective: Earn gold medals in all challenges.

Platinum:

Unbeatable Fist
Objective: Ruler of All.