Sorry, to correct you (but bett correcting than someone wondering about your calculation) , but in a 20:60 situation, the 20 has 25% chance of winning, not 33%. You have to add in the 20 attack points to the "100% chance" (does not exist!) as well, as was done in AOD-NEKO's example.
20 attack versus 60 attack = 20/80 versus 60/80 = 0.25 versus 0.75 = 25% versus 75%
Just my piece of adive is abilities vs abilities...so if you like to counter Uranus you should use Yayoi or someone who has stop ability...or if you want to counter Yayoi you should use some who has no ability like Nanook
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