Just to bring this up, Master Chief's survival from heights is attributed almost entirely to his suit even in the games by Cortana, the soldiers, and himself. The suit has a sort of liquid layer within it that takes almost all the impact of stuff. As for without the suit, the durability augments Master Chief has then are ceramic material grafted onto his bones to make them not break as easily, but even then, the material put on doesn't even exceed 3% his total bone mass.
So I'd say a double strength, double mass kick from Duke to the head to him? Even taking my realistic lowballing of Duke, if it's not breaking the skull, it's rattling the head hard enough to more or less smash his brain against the inside.
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