What's the word for “busting the myth”?

Solution 1:

You could consider "debunk"

To expose the falseness or hollowness of (a myth, idea, or belief).

Individual cases where a stereotypical assumption is confounded might be described as someone "breaking the mold"

Women Artists Who Broke the Mold

Solution 2:

Debunk is spot on but, if you don't mind being a little less accurate, dispel also works and I've seen it in this context quite frequently.

I am posting this in order to dispel the myths and rumours that answers posted three hours after the question never get upvotes.

Solution 3:

Disprove means "to show that (something) is false or wrong." So you could say, for example, "A recent study disproves the myth that girls are bad at sports."