The objectively correct ban is a top tier hero for your role that you don’t play, ie in 7.34d a support player might ban treant or grimstroke, a carry player might ban CK or weaver, an offlane player might ban spirit breaker or bristleback and so on, depending on what’s not in their hero pool

Personally though I’m currently banning AA/muerta/weaver kinda randomly because I’ve gotten pretty tired of playing against them so often