Atria Silversword
Right, so Atria's an officer, a soldier, and a mech pilot. She's also from an anime, which has her powered up enough that she's fast enough to keep up with somebody who can knock bullets out of the air. That said, she's professional to her core, which is both a blessing and a curse here. So, the first reaction would be a "What the hell?!" and possibly punching back. If it escalated from there, she'd go right to deadly force and a quick kill shot (again, professional soldier).
Princess Stellaria (aka Stella)
Stella used to be a combat support mage from a JRPG, but all those powers are long gone now and these days she's a grad student studying quantum physics. So, HER reaction would be to reel back and give a "What the hell?!" response and not hit back. That said, she's Atria Silversword's best friend, the two tend to be together when out and about, and punching Stella is a really good way to piss off Atria...who in a fight tends to default to deadly force. So...Stella reeling from the blow, possibly followed by a hail of explosive tipped bullets from Atria.
Captain Infinite
Captain Infinite is bulletproof. Your MC would probably break his hand...followed by Captain Infinite politely asking for a explanation (because he's basically a really friendly person without a malicious bone in his body).
And that's my three main characters.
