How to Survive as a Trash Extra Villain

I possessed a worthless extra who bullied the protagonist and got expelled after being "taught a lesson." It’s a small relief that I know the original plot, but the real problem is that this novel’s world is headed for destruction. There’s only one way to survive in this damned world: somehow help the protagonist and prevent the apocalypse. But all I get are looks full of contempt from everyone around me. “Hah, it’s too late to change the setting now…” Fine, so what if I’m alone? A villain survives using a villain’s methods. Protagonist or not—I’ll survive this my own way. — Description from novelcodex.org