A human character can literally be any character as long as they follow the following criteria. They should be imperfect. They should not be able to do things that no living human can do without the help of science fictiony gadgets or magic. They should have emotions and a personal history. They must be effected by their social background.
In any story there can be either human characters who act human and have human abilities, or nonhuman characters who don’t act human and can do things that are far greater than anything a human can do.