Store your refference or just the result somewhere easy to access like GameMode/GameInstance or even your Controller.
BeginPlay → getGameInstance → CastTo YourGameInstance → Set VariableNameYouChoose and pass self (YourBP or Component that has the Variable you want to get) or just the Result after you calculated it.
Inside your Fighter you get the Variable from there when you need it. No need for get all Actors of Class and it will work with dynamicly spawned Fighters out of the Box.
BeginPlay → getGameInstance → CastTo YourGameInstance → Get VariableNameYouChoose