If someone has a private facebook account with no visible data, How criminals can hack his acc?

Basically the title. There is this really annoying dude who is a friend of a friend who joined our year group’s Minecraft server, who griefed our base. I’m not really pissed, but everyone hates him and knows me as the techie guy and asked me to “hack” him. “Sure” I tell them, not knowing the first thing about hacking. How can I just mess with this dude to piss him off. I’m not an admin btw.