Amoral Combat

Amoral Combat is a side quest in the Fallout 4 add-on Nuka-World.

Detailed walkthrough
After completing The Grand Tour, the next time Nuka-Town is visited, a gang member will inform the overboss that a new challenger has reached the end of the Gauntlet, and they should go talk to Fritsch to find out what to do.

Locate Fritsch in the Nuka-Cade. He will say a new target has entered the Gauntlet and gives two options: allow them through to the arena or drive them out. Driving the target out prevents one from acquiring the gear the challenger had and automatically fails the quest. Accepting a fight means the player character has to face the challenger and beat them.

If one chooses to fight, head to the Cola-cars arena, meet the foe and best them to maintain the title of overboss.

This quest is repeatable, with a new challenger every time, culminating in the rogue knight who, upon defeat, will drop the unique weapon Aeternus.

After two or more in-game days, entering the Gauntlet from the arena end will activate the next opponent/phase of the quest.

Bugs

 * The quest may not start as intended.
 * To fix this, try to return to Nuka-World using the monorail and go through the Gauntlet again.
 * If the quest still does not start, the console command may start the quest. This can be repeated after each fight to quickly advance through the opponents.
 * After completing Power Play and defeating the rebel gang, this may cause a bizarre event to occur when entering the arena to fight the opponent. As before, members of all three gangs are present and a firefight begins in the stands as the two allied gang member spectators attack the members present from the third. This will continue, even if the player character begins the arena fight, until all rebel gang members have been dealt with. It may also freeze as well, making it impossible to enter the building at all.
 * After completing Open Season and after killing every raider in Nuka-World, it is possible to still participate in the ongoing fights. Upon entering the Cola-cars arena, all the raiders will appear hostile (marked red on map) but will not attack until the player character has defeated the opponent.
 * When the next opponent arrives in the arena, upon heading there, the mag-lock door will not be open, which prevents one from entering the arena to fight the combatant.
 * Reloading to a previous save should fix this.
 * In order to proceed, one can permanently remove the door by clicking on it in console mode and using the command . One can also float though the door by toggling collision with the command, but this is not a permanent solution.
 * Occasionally, the opponent may fail to actively engage the player character once they are in the arena, but they can still be attacked since their door is open.