The key to making an fighting game AI API interesting is enforcing the same reaction delays humans have, from decision making to input, which is roughly 250-300ms, if I remember correctly (your nervous system from brain to fingers has pretty high latency).

That delay time is what well-made fighting games are designed and balanced around. If you forced the AI to create inputs that would get processed however many milliseconds later they would actually have to start predicting their opponents, seeking hit confirms, etc.

If you don't enforce any sort of delay, making an unbeatable AI should be trivial.