An objection that comes up to Sola Fide is the idea that all you need to believe and that it doesn’t matter whether you sin or not. That is usually the thoughts of some atheists, Muslims, and Roman Catholics. Those that suffer from a doctrine of works salvation. The problem with their objections is it equally applies to their own positions.
In Islam, salvation is completely arbitrary and based on the baseless whim of Allah. It ultimately doesn’t matter whether you live as a saint or a devil. You’re in the hands of an arbitrary God.
In Roman Catholicism, you merely satisfy God with magical incantations and works. You could live a hellish life. You could be as holy as Hitler. As twisted as Ted Bundy. But a priest at the end of your life could baptize you in the Trinitarian formula and you’re magically saved.
In Atheism, your life was a product of cosmic events that you’re truly insignificant for. Your works amount to pleasing people that ultimately die and their likes and dislikes disappear. Good deeds are illusory by-products from our evolutionary upbringing.
So, Sola Fide hardly has any significant competition. For it is the worse theological soteriological perspective, except for all those other systems tried time and time again.