>>47953583So, the Elektross family is in the Slow EXP group. It would take at least about 300000 EXP to reach that level from when you caught it, maybe a little more if you caught it earlier. Given you're on Challenge mode, trainers will be a bit higher level, but with EXP scaling that hardly matters. I also assume based on your posting history that you used the Lucky Egg. Given all that, and the fact that again given your posting history you fight every trainer and like to overlevel a single Pokemon, I'm going to say that it's entirely possible your team got that imbalanced, if you want to give me a screenshot of your team.
Still, B2W2 is harder than XY, where you get a level 100 Arceus the moment you get Wonder Trade. After all, the game gives you the option to use it, why shouldn't you?