A Die Hard scenario with an alien in the lead. Some inspiration from Predator franchise. 

SYNOPSIS:

ALIEN WARRIOR

The Sampson family is preparing for a reunion, John Sampson arrives with his wife Terri and son Joel, meanwhile an alien ship lands and turns invisible and is hidden from view while the alien a warrior known as a Knulex arrives and must battle as a rite of passage arrives at the reunion. Meanwhile a gang of criminals led by Andon Lyle takes over the reunion to extort money from patriarch Frank Sampson. While on patrol, two of Lyle’s men are killed by the alien who believes worthy and scouts the area and runs into Joel and a few other kids, and convince the alien named Scux to help them. Scux manages to eliminate some of Lyle’s men and soon Lyle finds out someone else is there. As his men seek out the intruder, the kids learn about Scux’s people and learn that he must fight worthy opponents in combat as a rite of passage.

Lyle and the hostages realize they have been dealing with an alien warrior, and Lyle and his men take as much money as they can and soon run into Scux who takes many of them out, then goes after a fleeing Lyle and the two battle with Scux killing Lyle. Scux’s people arrive and upon learning that Scux took out a full unit of men accepts him and that he had passed his right of passage. The family thanks Scux who returns to his home planet.