This so typical. Villain is outmatched. Villain calls henchmen. Hero beats henchmen, who are lying scattered around in the room afterwards. Villain is still on his feet. Why? Bro, did you just call your buddies to ambush me? Then you are at least the second or third guy I try to give a smack down in this fight (, if possible).
And then those former S-Rank Adventurers. S-Rank. MC had no good development nor growth until now and he already faces off the elite? Does that make sense from a story-teller perspective? That's some inflation. I guess the author himself doesn't believe this manga will last long. Or is this also a LN adaptation? There are no links, so it doesn't look like it.
"Hi, I want to register as a new adventurer."
"Okay, fill out your forms. If you need help *blahblahblah*"
A bit later...
"Alright, everything seems to be in order here is your licence. You start as a A-Rank."
"WHUUT? Slow it down. I'm just a beginner level swordsman. I just want to collect some herbs and kill a few slimes to begin with."
"RESTATE THAT! SLIMES ARE THE PERFECT LIFEFORMS!"
"... collect some herbs and kill a few goblins to begin with. *tehehe*"
"That's right. A-Rank is our entry level. If you are strong enough you might advance to A+ level. ...And then A++. Followed by A+++, A++++, A+++++ and so on. It's based on the knowledge of an isekaied person. It's called IIII-Youuuu-Enenarji-Lablu. And if somebody in the Guild is whimsical enough, you become an S-Rank. No reason. Just for fun. And then it is S+, S++, S+++, SS, S++++,SS+, SSS, which can be weaker then S++++, depending on some reason, we still have to make up."