Shadow the Hedgehog is from the Sonic the Hedgehog game series. Though he is ageless, he still can be killed. He holds the title of the "Ultimate Lifeform" for this reason, though he also believes he is the strongest...at least, until he met the Saiyans.
His speed is equal to that of Sonic, but his ability to manipulate the Chaos Emeralds is also very profound. This is probably due to the Black Arms DNA he received on his creation fifty years ago.
He can use Chaos Control without an Emerald. He is also able to take on a suppressed Super form with less than seven Chaos Emeralds or a Chaos Drive.