Surtur is regarded as the most powerful physical threat in both the MCU and the Live Action Universes in general, along with the common misconception that he can planetbust which is super untrue. Anyways Hulk is the strongest hero yet and has had the feats to back it up but still the fandoms dispute, too stubborn to acknowledge that Thor isn't the strongest Marvel character. (I'd like to note that Scarlet Witch is superior to him in all categories save physical body) Now I will present to you why Hulk would body Surtur to literally take his crown and reinstate his title as most powerful hero yet.
First, tell me, what do you hear when you see Hulk? Incredible? Green? I say thee nay. Hulk is the Strongest There Is, and with his rage, the source of his power comes from his mind. Meaning the madder he gets, the stronger he gets.
Also, Hulk nearly kills Surtur on-screen.
You can even see Surtur's skull fractured.
And Hulk gets madder after this. The madder he gets, the stronger he gets. So how is Surtur gonna stand up to the guy who cracked his skull?
People say Thor can beat Hulk with the power of his Mjolnir or lightning, but you know what I say to that? Hulk is the strongest there is!
Thor literally had to tell Hulk to stop bullying Surtur and let him end himself in peace!
While Hulk was roaring here, Thor was hiding off-screen!
The difference between Hulk and Thor is this - while Thor can beat little Surtur, Hulk can beat big Surtur. Thor implied that they had to "let" Surtur finish his job right before Hulk attacks Surtur, meaning Hulk could have actually made a difference.
I mean, look at this scaredy cat's face!
Hulk has even knocked Thor out with a single punch!