Katsuyu is a slug, which means she is very slow, she isn't the attacking type and her acid isn't that fast.
Being a slug and being able to split up herself (reminds me of suigetsu) leads me to think her whole body is mostly made out of water.
The manga showed that liquid beings have a big disadvantage against Lightning, which means Katsuyus weakness is Raiton, Kakashis strongest nature element.
Imagine kakashi who was able to bond an arm of the Gedo mazo with raiden do the same with katsuyus neck.
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look at katsuyus neck its always up in the air, easily to reach with a raiden loop.
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The electricity would hinder katsuyu to split up while the ration loop around her neck is cutting through the soft flesh of katsuyu.(it must be like cutting through butter since raiden cut the tails of a v2 jin with no effort)
The other way is to distract sakura from katsuyu with shadow clones, finishing one by one.
Kakashi is the wrong opponent for sakura, his paralyzing abilities are a bad matchup against katsuyus liquid body and sakuras movements.