Big Hero 6's Baymax will be a baddie in Kingdom Hearts III
Kingdom Hearts III is set after the events of Big Hero 6. That means that Hiro has created a Baymax of his own, but there’s also one floating around within a portal.
The antagonist “uses the powers of darkness to manipulate the Baymax body that was left behind in the portal. As such, the old Baymax body left behind becomes a dark, heartless Baymax.”