Make the Delivery Boy Go Away
To make this long story short, the OP hadn’t met his GF’s dad for three years. He was away working overseas, but the OP had heard a lot of stories about the man. Many of those stories involved the dad being a master of martial arts. He was basically a guy that could snap you like a twig if you looked at him the wrong way.
Thankfully, the OP wasn’t snapped in half when they first met. In fact, the dad thought he was a delivery man since he brought a cake to their doorstep. He was even kind enough to ask his daughter to fetch his wallet so he could tip the deliveryman/BF.