The Avengers left in a rush, while the mutants still had to hold the apology session that followed, its theme being apologies to the various factions that had come to attend the banquet. Although this was clearly a setup, as the hosts, they had still failed to take proper care of their guests and had frightened them, so they could only apologize one by one.
However, the guests who still had not left did not actually mind that much. To put it plainly, how could dealing with mutants come without risks? They had already had the scare and shouldered the risk; running now would be unwise. If they stayed, at least they could make the mutants owe them a favor, which might come in handy someday.
There were quite a few smart people like that. For example, the envoys from the Divine Spear Bureau and Wakanda had both stayed, and even the people from Latvia had not left. Charles personally promised them that the mutants owed them a favor, and if anything happened in the future, they would do everything they could to help. It could be considered a blessing in disguise.
Do not be fooled by the mutants' poor performance on the island, struggling even to deal with a volcanic eruption. That was because the island itself restricted mutants; it could even restrict an Omega-level mutant down to Beta-class, and the eruption had been too sudden, so of course the results had been poor. But once they left the island, every one of them was a planetary-level powerhouse. Getting a favor from them was an unexpected delight.
Still, these people soon left as well, because they knew the mutants still had family business to deal with next. This matter was far more important than diplomacy. Anyone with eyes could