What does the phrase, "who with a single thwart blow cleft asunder a brace of hulking blustering giants" mean?

Well, this phrase is to be interpreted with how you believe it would be. Let's break it down. Let's start with the beginning of our sentence; "Who with a single thwart." What does the word "thwart" mean.
Thwart: (verb) to prevent (someone) from accomplishing something.
So, we have this so far;
"Who with a single prevented blow."

Onto the next part, "Blow cleft asunder a brace"

Lets dive into the words "cleft" and "asunder."
Cleft: (adjective) split, divided, in two.
Asunder: (adverb) into pieces, apart

All together we now have; "Who with a single prevented blow split into pieces under a brace."

Lastly, we will define "of hulking blustering giants."

Lets break down this one more.
When I see the word "hulking" I think of the Incredible Hulk. So let's dive into that word, and the word beside it.

Hulking: (adjective) large, heavy, clumsy.
Blustering: (verb) talking aggressively, noisily

So now, we should have interpreted this as "Who with a single prevented blow split into pieces under a brace of large noisy giants."

Based on what we have rewritten this sentence, what do YOU think this means? I believe that they're talking about someone in comparison to the giants.

Have a great day :-)

The purpose of a persuasive essay is to convince the audience that writer’s assertion is indeed valid or true.