The following is an axiom of meta-ethics:
Justice is a necessary component of a complete ethical theory.
Justice in this context is intended to have a specific definition rather than the more broad definition it is given in the context of political philosophy:
Justice is everyone getting what they deserve.
To convince you of this definition, I will point out that its contrapositive, which, of course, is logically equivalent, is certainly an axiom:
Not everyone getting what they deserve is not justice.
If you don’t agree to this statement, you are not talking about ethics anymore. To dispute this, you have to claim that a statement like “Samantha didn’t deserve this!” is not an ethical statement in any sense whatsoever… and you encroach upon the domain of nonsense when you do so.