10 Worst Things Jean Grey Has Ever Done
2. Misused Her Mindreasing Powers
Having mindreading powers always looks a little awkward. Being able to see inside people's deepest, darkest thoughts means you might see things you don't want to, and you can't totally blame the other person for that.
This is the crux of why Jean Grey's powers often leave her looking like kind of a bad person. Over comic history, Grey has routinely read people's minds when she really shouldn't have, and more often than not uses people's private internal thoughts against them.
Although there's far too many to name in one sitting, an especially controversial use of Jean's powers appears in All-New X-Men #40, wherein the hero-in-training tells a young Iceman she's read his thoughts and knows he's gay - despite the fact that it must also be clear from Bobby's thoughts that he's having some real issues with understanding his sexuality.
It has a positive end result, with Iceman eventually coming to terms with this aspect of himself, but it's still worth saying that using mind-reading powers to learn incredibly private secrets is pretty much the most unheroic thing you can do.