Ring IQ- This is bar none, THE most important attribute in the game. This is so important that winning with a lower one than your opponent is more difficult. 
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Chin- This too is important. Any time your fighting a boxer with more power than you have chin, protect it with in fight strategies like jab or smother. Risk going to the body for a couple of rounds and switch to jab or smother to try to protect yourself. I’ve lost a lot of money betting on a fighter who had the fight in hand until wrecked by a single punch in the tenth. Seriously. 
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Defence and Accuracy- After Ring IQ I try to find matchups where I have more of this combined than my opponents. 
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These are the main powers and it’s not even close. The following powers are somewhat useful.
Aggression- Good for boxers who are aggressive. (Funny how that works). Combined with a high Stamina- can help you rack up tkos. Think pressure strategy. 
On the canvas- Nice backup stat if you are knocked down. 
Power- I feel it plays a bigger role for the computer than me. Getting a KO is difficult even when mashing the KO strategy. I usually just end up getting a TKO anyway. 
Cuts- Nice bonus so you can fight more often, but I don’t even pay attention to it really. So far down on my list I need binoculars to see it. 
Takes punishment- This irks me when it’s high for my opponent, but I rarely get TKOed so I don’t pay much attention to it. 
Dirty- Honestly zero clue. ?
Conditioning- I guess high is better than low but I treat it like cut.
Intelligence and dedication- zero clue.