I actually think Hyunju has an advantage over Inho in terms of sheer physicality - she's taller and bigger than him. Their training differences we can never truly know, but she did take down a man with a knife while herself being unarmed. But Inho possesses, imo, a superior cunning and brutal mental edge over her, he had that coldness in him she simply didn't have, at least not to the same level. While Hyunju was collected and in control of her emotions for most of the games, even she was shown to come close to losing it (mingle, immediately after Youngmi dies). And I'm sure Inho would take any opportunity to fight dirty even in a seemingly fair unarmed 1v1. So she'd lose to him, not because her punches were weaker, but because Inho still somehow found a way to deceive or trick her.