Only one??

Damn. That's tough to pick, 'cause I have several.

But if I could only make one choice, I would completely overhaul the judging system in boxing. Make judges accountable. Too many judges get away with lousy decisions or outright robberies. After two guys spend months in the gym, in sparring, sacrificing their families and their time... it's ludicrous that they should get shafted by corrupt and/or inept judging. Make judges accountable. Plus maybe increase the number of judges to five. Who knows. May or may not be practical. But the more eyes on a fight, the better and more possibility of a fair outcome.

You said one, so I'll stop there.