Suppose agent A has goal G, and agent B has goal H (assumed to be incompatible). Put both agents in the same world. If you reliably end up with state G, then we say that A has greater optimization power.
Fitnesses are dependent on the environment, though. So: if agent A has goal GA, B has goal GB and C has goal CG, and A and B produce GA, B and C produce GB and C and A produce GC then you can’t just assign scalar fitnesses to each agent and expect that to work. That could happen with circular predation, for example.
If you do want to assign scalar fitnesses to organisms—in order to compare them—I think you have to do something like testing them on a standard suite of test environments.
Fitnesses are dependent on the environment, though. So: if agent A has goal GA, B has goal GB and C has goal CG, and A and B produce GA, B and C produce GB and C and A produce GC then you can’t just assign scalar fitnesses to each agent and expect that to work. That could happen with circular predation, for example.
If you do want to assign scalar fitnesses to organisms—in order to compare them—I think you have to do something like testing them on a standard suite of test environments.