Question

should there be a comma before the highlighted word?
reverse-flash knew a shortcut so he got to the party before the rest of his friends.
add a comma dont add a comma

Explanation:

The word "so" here is a coordinating conjunction that connects two independent clauses ("Reverse - Flash knew a shortcut" and "he got to the party before the rest of his friends"). When a coordinating conjunction (for, and, nor, but, or, yet, so) connects two independent clauses, a comma should be placed before the conjunction.

Answer:

Add a Comma