determined in character, action, or ideas (Cambridge)
strong and determined (Oxford)
His resolute leadership was admired by many.(Oxford)
He became even more resolute in his opposition to the plan. (Oxford)
Their resolute opposition to new working methods was difficult to overcome. (Cambridge)
Resolute leadership
Resolute in his opposition
Determined
Headstrong
Irresolute
Undaunted
Resolutely
Resoluteness