I disagree. I take extremely frail to mean that he's like an old person in critical condition. Frail meaning his health is terrible.
Let's say you're right though. Duke probably isn't aware that he's frail then since he's apparently performing at peak health.
Duke: BALLS OF STEEL am I right? High five Chief!
*Chief high fives Duke, killing him*
or...
Duke: Ooh a suit... I like that kind of classy girl. Take it off and shake it baby!
*Samus kicks Duke in the crotch, killing him*
or...
Well the possibilities are endless. And they spell disaster for the Duke.
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No problem!
This is a cute and pop genocide of love!