unyielding

She had planned to be stern and unyielding in her demands, but the admiral’s compliments caught her off guard, as did his reference to poetry.

Your father wants to do things his way, in an unyielding manner.

I asked one western diplomat why Ukrainians were so unyielding.

We can certainly understand that she’s supposed to come off as ardent and unyielding, even surmising that she’s unsure of how to love anyone else because of how improperly she’s been loved herself.

"There's a great deal we can learn from their determination, their vision for scale, and their unyielding belief that we can create a better world."