Obstinate
/ˈɑːbstɪnət/ adjective mediumStubbornly sticking to an opinion or course of action despite pressure to change.
The obstinate toddler refused to wear anything but his dinosaur costume for a week.
Memory Trick
Shares the Latin root 'stare' (to stand) with 'obstacle' — an obstinate person plants their feet and stands firm, an obstacle no one can budge.