im sorry but i have to do this (spoilers ahead)
Luigi – Clear Adventure on at least normal with Mario
Jigglypuff – Clear Adventure on any difficulty with any character.
Cloud – Complete 100-man melee with any character.
Crono – Clear 3-minute Melee.
Naruto – Clear Adventure with the original 13 characters.
Shadow – Clear Adventure with Sonic, Tails, and Knuckles
Super Sonic – Clear Classic with Sonic on Very Hard Difficulty without getting Game Over.
Zero – Clear Adventure with Megaman getting Game Over on at least Normal Difficulty.
Young Link – Clear Classic with Link on any difficulty.
Inuyasha – Clear Adventure without losing any lives.
Mr. Game and Watch – Clear Target Test with every character but him.
Mr. Incredible – Clear Classic Mode with the original 13 characters.
Mewtwo – Clear Adventure with Pikachu and Jigglypuff.
Lloyd – Clear Adventure with any character after having one hour of total play time.
Blue – Clear Adventure with Blade on at least Normal difficulty.
Stages:
Final Destination – Unlock every character
Battlefield – Clear All-Star Mode with any character
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its a very great game ive been waiting for another SSBM game and i wouldnt think it would be on PC or newgrounds i am sorry for giving out the spoilers tho.