Before I proceed, I'd like to let you know that:
The specific string seen in your keyword is often a byproduct of automated search bots or "leeching" scripts that have been encoded. In URL encoding, %21 represents an exclamation point, so the query is essentially looking for "Index of Mp4 !!BETTER!!". This is frequently associated with cracked software, high-quality movie rips, or specific pirated content bundles. The Appeal of Open Directories Index Of Mp4 %21%21BETTER%21%21