Worst Jump the Shark in X-Men: Breaking Up Cyclops and Jean Grey
If there has been ANY chemistry that kept X-Men going IMO it's the chemistry of Cyclops and Jean Grey. The two were really somewhat made for each other despite the troubles, they somewhat made it back. And of course their romance was "until death do us part". I personally wanted them to have a real, cohesive relationship and plus, I always thought of it that they were truly meant for each other. However the writers were just so DUMB as to the point they actually had to KILL Jean Grey rather than fix the relationship. So I was already upset that Cyclops would have a love affair with Emma Frost and when reconciliation could be possible, the authors had to kill Jean Grey and later pair him up with the third party. I personally thought that perhaps there is a lesson to help couples cherish their moments before it's too late.