General:
* Persistent: This word emphasizes continuing despite challenges.
* Determined: This word suggests having a strong will to succeed.
* Resilient: This word emphasizes the ability to bounce back from setbacks.
* Tenacious: This word implies holding onto something with great effort.
* Unwavering: This word emphasizes a lack of doubt or hesitation.
More specific:
* Indomitable: This word implies an unyielding spirit, a strength that cannot be broken.
* Unflinching: This word emphasizes a lack of fear or hesitation in the face of difficulty.
* Relentless: This word suggests a constant and unstoppable effort.
* Unyielding: This word conveys a refusal to give in, to accept defeat.
The best word to use will depend on the specific context and the desired tone.