I saw the cartoon version of this.
From the new one, I mean. And it was awesome.
It was basically the turtles taking on the entire foot clan and kicking ass, beating everything from grunts to attack robots to three ugly Shredder clones (it's never really explained why Shredder had three ugly Shredder clones lying around, but so it goes) The final fight with the Shredder deviates a lot, naturally, but the ending is very similar, with Leo cutting off Shredder's head. ONSCREEN.
...and then we later see the Shredder get up and walk away. With his head under his arm!! It was one of the most memorable battles I have ever seen in any media.