It is not the most powerful heavy rocket in the short term. SpaceX Heavy falcon generates slightly more thrust at 1.7 million pounds at sea level compared to 1.67 million SLS, and both are well below 7.89 million pounds of Saturn V first stage. It’s also more expensive than some offerings, at $ 2 billion per launch compared to $ 90 million for the highly reusable Falcon Heavy and $ 350 million for ULA’s Delta IV Heavy.
However, SLS is also on its way to being one of the best performing platforms. A mission can carry payloads that may require two or more launches, even for SpaceX’s next spaceship, not to mention the existing options. This could save NASA money and greatly simplify some missions. It’s just a matter of how often you’ll see SLS in action – the incoming Biden administration having to delay the Artemis program, it might not be used as much as you expect.