What do think is the worst try at a gerrymander in Us history. My nomination goes to these maps from arkansas, made by democrats also.
House map
Senate map
Congressional map
Especially the legislature maps here. The districts that were eliminated should have been Republican ones and they should have tried to stitch together as many Democratic districts as possible in the Northwest while packing fast growing Republican areas into just a few districts.
Remember, Democrats as recently as 2008 held over 75% of the seats in both Houses here. They could have easily drew themselves safe majorities like Republicans were able to do in blue leaning states like Wisconsin, Pennsylvania, and Michigan.