There were differences between people.
There were also differences between the spells different people cast.
Harry had never felt this very keenly before, but now he felt it profoundly.
The lightning he produced with his Weather Charm-Lightning Charm was only as thick as his thumb, or as wide as the mouth of a cup at most. But Professor Flitwick's was as thick as a bucket.
Yet even when such a powerful Lightning Charm struck the monster, although it could hardly be called a mere tickle, it really did not have the desired effect.
The monster recovered completely in an extremely short time, until there was not even any sign that it had been injured.
"Severus, sorry for the trouble." After Professor McGonagall inflicted extensive injuries on the monster yet again, only to watch it recover in an extremely short time once more, she had no choice but to change her approach.
"Follow the route the monster came from and see if you can find where the ritual took place. If there's a magic array or anything else, try destroying it. Just fighting it like this doesn't seem to be working."
"All right," Snape replied without another word. He turned and ran toward the opening the monster had smashed through on its way in. After two strides, something resembling a puddle of water seemed to appear beneath his feet.
It let him slide a considerable distance with every step, which was quite remarkable.
"Why isn't Snape using that spell that turned him into black smoke earlier?" Harry was a little puzzled to see Snape actually running on foot.
Harry had never seen the spell Snape had used to turn into black smoke before, nor did he know what it was. But it looked very useful, and it was clearly much faster