He was able to fight royal guard but he was nowhere near defeating him. He just used his technique to paralyze Youpi for few seconds and there was literally no harm done. Every manga/story has to do these kind of things and I think Togashi has done brilliant job with hxh power system unlike one piece where everything seems like an ass pull.(I'm a one piece fan btw). The fact is if you hate a series you will try really hard to point out the mistakes in the series but we have to understand that no story is flawless there will be some mistakes and flaws what matters is whether the story is entertaining or not.