“Power” is so relative.
Strength in the One Power, based on how much one could draw, is well established in the literature.
Ability to weave multiple flows, or weave in novel, quick or creative ways is also established and considered as important as raw strength. For example, Lanfear could not match Ishamael in brute force, but they were considered equal in strength sometimes in the books.
Strength in Tel’aran’rhiod is irrelevant of strength in channelling. Bair could entirely outclass Nynaeve despite having no ability to channel at all, whilst Nynaeve is able to channel more of the One Power than most other characters.
If looking outside of the “magic”, the Ta’Veren and the people who influence them should also be considered.
Perrin’s charisma (with his wife’s help), Demandred, Messana, Rhavin and Sammael politically. Min as a philosopher… Aludra invented artillery, and with Mat, crossbows and modern warfare.
At a really basic level, I think you’d have to look at “who has to be in the story for it to end the way it does”
And then I think we would have to quote the authors and say “it was about them all.”