The weak at fighting part.
That part is mainly about him being all talk no action which's very surprising for 1- an admiral 2- a top tier all together
Problem is Issho has been put to the test multiple times and either looked lackluster or bad outright ; he doesn't have the same excuse dragon or some other top tiers have where they didn't get real shots
Issho's showing at Dressrosa in retrospect is still disgraceful even if you say he held back to let Luffy shine ; doesn't excuse him not being able to stop the birdcage
and you can say thats plot convience cause Oda wanted tension for the luffy fight and a timer ; but then whats the excuse for letting Jack go ? and Jack clearly not an important character in Oda's eyes looking at how he treated him after that , he could've easily had Issho bag him just like Aramaki bagging King Queen Weevile
But he wasn't given to do that either then later his latest showing is again really bad as he fights Revos whilst handicapped like Aramaki , still doesn't excuse to either of them and if you are a sweat scaler some ppl pointed out after the Issho vs Aramaki fight , Issho is bandaged and didnt do anything after it while Issho went to wano and did more individually
He just needs to prove himself individually , you can't just slap admiral sticker on him and call it a day