I am a little confused, because it says “your chosen poet” but you mention Shakespeare.  Are you comparing Shakespeare’s poems to another poet’s?  Are you talking about Shakespeare’s “Sonnet 21” and so on?  “Sonnet 21” is not about power necessarily, but you could say it is about the power to be yourself and not worry about what others think.  Likewise, “Sonnet 71” can be interpreted as taking power in a powerless situation, when one is dead.  Of the three, I think “Sonnet 91” might be your best bet, because it too has a focus on strength, or power, through love.