Not Jim Sterling said:
My suggestion is his power will work on wherever he being barely outclassed or immensely outclassed but the effectiveness of his power will be reduce.
I partically agree with this.
If his opponent immensely surpasses him in ALL regards, meaning none of Yhwach's hax, techniques, AP, Speed and other stats can help him at all, then his Almighty's effectiveness should be reduced to 0 due to no futures Yhwach can forge to help him win in any way.
If its someone who barely outclasses Yhwach, then yes I agree Yhwach could still use Almighty to beat them, it just becomes more weaker and limited due to lesser possibilities for Yhwach winning.