John Donne's sonnet "Death, be not proud" utilizes strong diction in several places. One interesting thing about the diction of this poem overall is that although the subject of death would normally elicit negative diction from an author, Donne uses mainly positive diction. Also, death is not only the topic of the poem—Donne also makes death the audience of the poem through the use of apostrophe. Therefore, the diction that he uses is all the more powerful in the context of his directly addressing death and challenging death's very personality.

Positive diction is seen is in lines 7–8, when Donne says, "And soonest our best men with thee do go, / Rest of their bones and soul's delivery." Here, Donne is describing death as a peaceful deliverance for those who face it; therefore, it does not deserve fear or dread. This idea is further reiterated through his language in lines 13–14, when he says, "One short sleep past, we wake eternally / And death shall be no more."

He continues on from line 8 to challenge the idea that death may think too much of himself, and it is in this section that Donne chooses words with negative connotations to communicate his thoughts about how truly powerless death is. Line 9 says, "Thou (death) art slave to fate." The choice of the word "slave" has such a strong meaning that Donne is able to clearly demonstrate the position that he believes death holds.

Donne's poem "Death Be Not Proud" is really an 'in-your-face' kind of poem.  He deliberately chooses very strong adjectives like "mighty" and "dreadful" to describe Death in the opening of the poem only to turn around and recant those words in the same line.  It's a slap in the face of Death.

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The first thing that came to mind when I read your question were the lines,

Thou art slave to Fate, Chance, kings, and desperate men,
And dost with poyson, warre, and sicknesse dwell,

Here, the poet is using personification by speaking to death itself. The most important word in this section is "slave," because the poet is bringing death down a notch. Death is, in fact, used by Fate, Chance, kings and desperate men. We don't usually think of death as a slave, but as something that wields power over us. Donne's word choice gives us a new way of looking at death.