More particularly, how one crafts a poem of extremes without sacrificing tension. That is, it seems obvious to me, the pitfall: a rant pushes against logic and conclusion, it is an apostasy of anger. And the poem that praises dares against effusiveness and sentimentality.
Here's my favorite poem of praise, the one that I go back to as the instructive.
Praise to my older brother, the seventeen-year-old boy, who lived
in the attic with me an exiled prince grown hard in his confinement,
bitter, bent to his evening task building the imaginary building
on the drawing board they'd given him in school. His tools gleam
under the desk lamp. He is as hard as the pencil he holds,
drawing the line straight along the ruler.
Tower prince, young king, praise to the boy
who has willed his blood to cool and his heart to slow. He's building
a structure with so many doors it's finally quiet,
so that when our father climbs heavily up the attic stairs, he doesn't
at first hear him pass down the narrow hall. My brother is rebuilding
the foundation. He lifts the clear plastic of one page
to look more closely at the plumbing,
-- he barely hears the springs of my bed when my father sits down --
he's imagining where the boiler might go, because
where it is now isn't working. Not until I've slammed the door behind
the man stumbling down the stairs again
does my brother look up from where he's working. I know it hurts him
to rise, to knock on my door and come in. And when he draws his skinny arm
around my shaking shoulders,
I don't know if he knows he's building a world where I can one day
love a man -- he sits there without saying anything.
I know he can hardly bear to touch me.
----Marie Howe, from What the Living Do.