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.
Canon Defilement: Aside from the obvious Alternate Character Interpretation going on for just about anyone, the actual fanfictions tend to get a lot of the technical facts from the books wrong(such as the length of time between the forming of the Riders and the Fall), and in some cases flatly changes them.(Such as the name, color, and gender of Eragon I's dragon.)
Complete Monster: Taranis, who regards dragons as nothing more than weapons, enslaves Silarae with psychic torture, uses her as leverage to ensure Ravana's good behavior, feeds them condemned criminals, executes enemies who surrender, and eventually holds their last remaining egg hostage.
Like You Would Really Do It: Galbatorix has several close brushes with death during From White To Black most notably late in chapter fifty-six. But then you remember that it's a prequel story...
Moral Event Horizon: Vrael crosses spectacularly when he suffocates a baby just because it's of Mixed Ancestry. Where the Riders as a whole stand on the moral event horizon becomes clear when their long history of genocide is revealed (and again when it's demonstrated during the dark elf incident.)