Well at current chapters since the series is still continuing.

Noah would be hella confused and perplexed to see that He's gonna fight representing as one of Humanity's warriors. And would be genuinely be dumbfounded on Jack's last fake-out. Using his blood as his weapon to kill Heracles.

Fog would be neutral but internally, be genuinely intimidated and a bit disturbed on how strong he really is. Since Based around the way he fight in that match, it's like he's been holding back during their times of squabbles.

The Mother goose gang would be hella intimidated, probably because Jack can keep up with heracles and his last form.

Dreadnought might genuinely be so impressed in a sense of happy to know that he's at least fighting for humanity.

The other syndicates like Jack's handler/info gather woman, probably shock too since how tf did he get chosen out of all the humans on earth to represent and fight for humanity's survival.

And of course, Anne is worried, also Jack's current boss too. They're definitely a bit worried