I can't believe you made yourself a bigger target. Did you honestly think that bigger would be the better?
Are you telling me a regular Shredder can survive a seven story fall and a dump truck crushing him, but a Super Shredder can't survive a bunch of wood falling on him?
It has that depressingly common problem in games nowadays that the giant boss fights are all really fucking easy... the actual fight is just a huge lumpy mess winding up its attacks for so long that we've got time to prize off the dodge button, flick it across the room and recover it from between the sofa cushions before we actually need to press it, and then it gormlessly zones out and lets you whale on its obvious weak point for thirty seconds.
When the big boss expands like an asshole in the prison showers and takes on his city destroying form, my first reaction should not be, "Phew, that's a relief."