Before that panel, I would have never bet on any Zhao battle being the #1 meat grinder for Qin in the entire manga. I mean in the future you've got the gigantic Chu wars and everything else. But it's possible I guess.
"While the Battle of Hango had the most recorded Qin casualties of any battle of the Warring States period, the Battle of the Chu territory, Bad Haircut Land far exceeded it in actual casualties, mostly left off records"