"Unshakeable" means being unable to be moved or affected by something, usually referring to one's beliefs, confidence, or determination. Full definition
And Davison claims that he got the same sense of unshakeable belief from all the players he spoke to, with Kieran Gibbs suggesting that the transfer of Petr Cech from Chelsea has had a really big effect. (justarsenal.com)
It's fleet of foot, it changes direction quickly and assertively and its grip on the road instils its drivers with unshakeable confidence in the car beneath them. (motoring.com.au)
They stand several generations apart but are driven by the same unshakeable conviction in education as a fundamental human right that should be enjoyed by every child, regardless of their circumstances. (globaleducationmagazine.com)