These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Nightmare Fuel: "Lady Lazarus", "Daddy", and a bit of "Crossing the Water" too. They are beautiful and incredibly potent emotionally, but they're terrifying. "Cut" could count as well, mostly because of the cringe-inducing imagery.
This is Number Three. What a trash To annihilate each decade.
True Art Is Incomprehensible: The Colossus. Most of the poems will require you to sit down and think about what the hell she was really talking about along with looking up words, phrases, and obscure shout outs; as an example, the second stanza of "Two Views of a Cadaver Room" describes a 16th-century painting.
Vindicated by History: She was a respected, though not very well known, poet in her day. After her death, she became a bestselling author, won the Pulitzer, and is recognized as one of the most influential poets of the 20th century.
The Woobie: Felt abandoned when her father died when she was eight, worried that she would never find the right man that wouldn't force her into the kitchen for the rest of her life, suffered from severe clinical depression for years, faced countless rejections for her poetry and prose, felt unloved by her mother, had a miscarriage, her husband, renowned British poet, Ted Hughes, left her in October 1962, and then she committed suicide in February 1963. It's really easy to wish you could have given her a hug.