This page of our guide dedicated to Fallout 4 Nuka-World shows how to complete the side quest Immoral Combat. An individual has entered the Arena, and you must get rid of it to amuse the looters.
This quest starts after completing The Big Visit quest. As you walk through Nuka-Town, one of the looters asks you to go see Fritsch (picture1). Enter the Nuka-cade to chat with Fritsch (picture2).
1 picture
2 picture
If you want to free the man or refuse to fight, the quest fails, so choose to fight (picture3). Then enter the Cola-Cars track and stand on the bumper car track (picture4).
3 picture
4 picture
As soon as the door opens, eliminate the competitor to complete this quest. Note that this quest can be reactivated randomly during the game, offering you the opportunity to face new competitors.