Obstinate
Part of speech: adjective
Definition: Stubbornly adhering to an opinion, purpose, or course, usually with implied unreasonableness; persistent. Said of inanimate things not easily subdued or removed.
Example sentence: What is exciting is not for one person to be stronger than the other... but for two people to have met their match and yet they are equally as stubborn, as obstinate, as passionate, as crazy as the other.
Determined
Part of speech: adjective
Definition: Decided; resolute.
Part of speech: verb
Definition: To set the boundaries or limits of.
Example sentence: There is no chance, no destiny, no fate, that can circumvent or hinder or control the firm resolve of a determined soul.