I would say wbc
If you're referring strictly to the Alphabet groups, the WBC is still the largest. However, there is not much distance between the rest because the general public can't decipher one from the other.
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In the past, during the days of just the WBC and WBA, the WBC still carried more clout as the WBA was based in South America and showed heavy bias to South American fighters. The WBA might have been more powerful had there been more noteworthy fighters from that region at the time.
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Today, boxing is primarily run by the promoters, not the sanctioning bodies. If Bob Arum wants to put Manny Pacquiao against one of the champions of ANY of those organizations, he will. And Pacquiao will fight whomever Arum tells him to.
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If Floyd Mayweather decides he wants to fight a champion of one of the organizations, he will. And the promoters, unless it's Arum, will do whatever must be done to make that fight happen.
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As for any other fighter -not named Mayweather or Pacquiao- it depends on who his promoter is. Top Rank and Golden Boy are the premiere promotional companies in the sport. Don King is no longer a factor and there are very few who wield any power, outside of Mayweather.
The WBC is still the biggest. But even they will do what the promoters tell them to do.
I don't know what you mean. Like alphabet belt or promotion?
Alphabet belt: Doesn't really matter, the four major belts are WBC, WBA, IBF, and the WBO. The WBC is by far the most recognizable and famous belt.
Promotion: The two major and most significant promtions in the sport are Golden Boy and Top Rank. Both are US based, have the best fighters, and put on the most fights.
Stick and Move said it
The most well known you know the one every boxer works thier entire career to get to
