He's not fighting them. He's burying their souls. Having a planet destroying robot, or even a galaxy destroying robot, does nothing to protect you against the touch of death.
Cheap as fuck, sure, but that's why Bleach vs. anything makes for a really stupid powerlevel discussion: a nameless background shinigami recruit with no training will still win by default against any character unless they fight ghosts.
What's that? Your character can level mountains by glaring at them? That's very nice, enjoy your trip to the afterlife.