Warning: major character death (i.e. please note the cover picture). This might be considered AU, though not necessarily. "You" and "he" are interchangeable between Bruce Wayne and Clark Kent—or, perhaps more accurately, Batman and Superman.
(In all honesty, they're pretty interchangeable between many other pairs of best friends and/or brothers—as canon, if one dies in canon, or AU, if one doesn't—though some fit better than others. So you could think of Aragorn and Halbarad, if you like, or Harry and Ron, or Roland and Oliver, or Peter and Edmund, or Kirk and Spock, or Steve and Bucky, or Anakin and Obi-Wan, or even Woody and Buzz Lightyear, if it take your fancy.)
Did he not give enough, 'ere he had fallen?
Have you yourself not felt sufficient pain?
And now he lies here, dead—and for what reason?
You're powerless to bring him back again.
Yet this, perhaps, is how he would have wished it:
To die now in the cause for which he lived;
And yet your heart cries out, rebels against it;
You would not trade him for the good he did.
Your gaze is captured in his shattered visage;
Around his broken corpse you clench your fists;
The battles rage—you cannot spare a minute,
And still you cannot tear yourself from this.
His life too short to end in such a manner;
His works and wishes, as his life, are gone;
His family has lost its head and leader,
And you your friend—how will you all go on?
And yet he would not wish his death the ending,
As you would not, were all of this reversed:
He'd want you to stand up, keep living, loving,
Still wage the endless war that claimed him first.
And for your friend and brother you will do this:
Arise to live your life, though he cannot;
His fall you'll mourn, his memory you'll cherish,
And in his honor fight the war he fought.