Knock out
The next two weeks went by and all these days, candidates didn't give up at all.
They are trying to replicate the void technique. They are trying so hard actually.
But unfortunately, there is not much progress. After all, it would be hard for them to suddenly gain this much control in such a short period of time.
The major powers although powerful, only teach their disciples in the conventional ways and according to them, the bigger the spell, the bigger the technique, the more damage it does, the better it is. They generally, wouldn't account for the disadvantages and backlash of the technique.
So, these candidates although chosen didn't get their training from God's themselves, they are only trained in these major powers and in the same ways.
They will learn the importance of control and efficiency of the spell or a technique when they truly meet a person who is a suitable rival.