Zero

Zero is a playable 3rd Party unlockable in Super Smash Flash and Super Smash Flash 2 from the Megaman universe He is unlocked on Super Smash Flash by playing Adventure Mode with Megaman on Normal of above without continuing.

SSF
In Super Smash Flash, Zero's sprites were ripped from Megaman X3.

SSF2 Moveset
In Super Smash Flash 2, Zero's sprites are recolored from the Megaman Zero games.