The One Who Administered the Challenge
The lightning contained a huge amount of Magic Power as well as the Lightning Order, so even Theo wouldn't be able to contain it that easily. At the same time, removing the Order meant that he would be removing the trial itself since it was the test of might.
Hence, Theo planned to use all his strength against this lightning without removing any of it.
As soon as the Irregular Guardian in the spear form struck the lightning, it caused a huge shock wave that dispersed the lightning.
At the tip of the spear, there was actually a concentrated Magic Power that Theo gathered with the help of Enhanced Concentration Capacity. Although Theo wanted to use that Magic Power to penetrate the lightning and disperse it, the lightning looked alive. Even if he dispersed it, the lightning would just fuse again after they slipped past the Irregular Guardian.
Hence, the Magic Power dispersed them to the point they couldn't join together anymore.