As the title says.
If you don’t know the discworld books by Pratchett, Granny Weatherwax it the most formidable character. She is a witch, but doesn’t generally use magic to solve problems; preferring to use persuasion and manipulation. In saying that her magic is extremely powerful.
Maybe a bard with huge wisdom, persuasion and intimidation.
I’d go with druid. It gives you a reason for high wisdom and the aspect of merging with animal minds. High Charisma for persuasion and intimidation, probably a background supporting intimidation.
The fact is that she can do super impressive magic, she just usually chooses not to, so you’d definitely want to go with a full caster.