When does culture, especially at the junior levels, impact performance?

Maybe I've been watching too many TED talks on leadership over winter break, but I got to thinking if any monkeys had examples of where firm culture, for better or for worse, really impacted performance (or even returns) in PE?

I'm especially interested in the associate / principal-VP dynamic. Do you guys have any examples where a toxic relationship translated to worse firm-wide performance, or where a collegial / friendly environment led to outsized returns? My working thesis for a while has been, becaues of the high turnover and relatively commoditized work at the associate level, the usual leadership theory out there about effective middle managers sacrificing for or looking out for their juniors may not be as applicable, but I would love to be proven wrong by some sweet anecdotal data or conjectures from your guys' firms.