Compared to characters from a lot of other fictional worlds, Potterverse wizards are very powerful, sometimes even overpowered. There's no mana requirement to their magic, they can cast as many spells as they want without tiring significantly. They can teleport, become invisible, read and control minds, have an insta-kill spell, can modify or erase memories... Whenever a crossover story is written with HP and another fandom, authors introduce ways to even the "playing field", usually by having the HP character lose their wand or the other fandom's characters be somehow resistant to magic. But, surely, there's some enjoyment to be had in a scenario without equal chances. How about the wizard doesn't lose the wand? What if the other fandoms aren't immune to Potterverse magic? I personally have no problems with stories where wizards are clearly way more powerful than everyone else, provided these stories are written well. Say Harry Potter appears in Westeros and wrecks everyone's shit. Now, you may claim that such a quick-win would be boring, and that may be true to an extent. Harry may not even want to use the Imperius, or get involved everywhere. And even if he does, so what? What happen AFTER he gets involved? He's clearly just one guy, who while powerful still won't be able to be everywhere at once. Or how about Voldemort finding himself in the Star Wars universe. Granted, Sith Lords like Darth Sidious or Darth Revan could resist the Imperius thanks to the Force, but something tells me they wouldn't resist the Killing Curse. But again Voldemort is just one person, and the Galaxy is a big, big place. My point is that curbstomp stories can be fun, they just have to be done well.