I'm not sure how big the Death Star is (because I don't know shit about Star Wars), but maybe a Reaper from Mass Effect? They seem like they'd be tough as hell to kill.
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No, the Death Star can destroy worlds (53 quadrillion megatons), it has enough energy to destroy all Reapers. Also the Death Star is 160 km wide.
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"I'm Commander Shepard and this is my favourite store on the Citadel."