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.
For the Comic Book
Base Breaker: Sam Alexander. While some fans have been willing to give him a chance, others don't want anything to do with him.
Richard Rider himself for the Marvel Universe in general. He was originally a C-list version of Green Lantern before Keith Giffen and the duo Dan Abnett and Andy Lanning turned him into a major character in the cosmic side of the Marvel Universe and gained a cult following among Marvel fans.
Growing the Beard: Some fans thinks Sam's series is starting to get good thanks to Gerry Duggan's writing.
Marty Stu: Some Rider fans accused Sam Alexander of this simply for existing despite the fact that by all logic he couldn't have his powers, since most of the Nova Force went missing with Richard Rider, along with the fact that his father was part of a super-secret bunch of special ops Novas that conveniently have never been mentioned or hinted at before.
Memetic Mutation: "I pulled him inside out and saved the universe. What have you done lately, X?"
Dan Abnett and Andy Lanning — their take on the character forced everybody else to stop treating him as an inexperienced rookie.
Gerry Duggan for Sam Alexander.
Nightmare Fuel: The Knowhere story in vol 4 is all kinds of disturbing.
Knowhere itself is pretty disturbing. A decapitated Celestial's head floating at the literal edge of the universe.
The most recent version of Richard's heroic sacrifice in the Cancerverse shows that the Revengers version of Captain America cut off Richard's arm with his shield. Previous sighting of dismemberment in the Cancerverse have almost always resulted in the victim regenerating into a Body Horror.
Tearjerker: The death of Ko-Rel, along with all her friends, co-workers and associates, which all happens in the space of a few days.
For the Novel
Incest Subtext: Prince and Ruby Red's relationship can start to look a little... iffy. Let's not forget that Ruby dies from anaphylactic shock after kissing her brother's corpse; apparently quite, erm, passionately, since she was killed almost instantly.