Who has the most power in The Crucible?

It would be Abigail Williams.

Explanation:

She was the one that orchestrated it all, which costed the many lives of innocent women to be hanged for being accused of witchcraft.

She used people & manipulated her way into court, causing mass hysteria for something that wasn't even true. She had power over the young girls which if it wasn't for them she wouldn't have been able to go through with her plan. She is the reason of why everything happened the way it did.