I saw Echinda... so

Here I come, rougher than the rest of them.
The best of them, tougher than leather.
You can call me Knuckles. Unlike Sonic, I don't chuckle.
I'd rather flex my muscles.
I'm hard as nails, it ain't hard to tell.
I break 'em down whether they're solid or frail.
Unlike the rest I'm independent since my first breath.
First test, feel the right, than the worst's left.