steely-eyed

steely-eyed (comparative more steely-eyed, superlative most steely-eyed)

1. (idiomatic) Having a hard, strong, and determined look about oneself.
2. (idiomatic) Having a hard, strong, and determined mindset / mentality.
   • 2019 April 14, Alex McLevy, “Winter is here on Game Of Thrones' final season premiere (newbies)”, in The A.V. Club‎:

     Her steely-eyed control of emotion has become such a reliable source of strength and enjoyment in the last two seasons, it’s genuinely moving to see her defenses fall in the face of long-lost friends and family.

• steely-nerved
• steely-spined
• diehard
• hardcore
• tough as nails

• steely-eyed missile man

• sharp-eyed
• clear-eyed
• bright-eyed