1. The Luis Arraez trade.
Probably the biggest knock on Peter Bendix is of course the Luis Arraez trade. The narrative goes that Bendix was in such a rush to sell-off the team, that he moved Arraez to the San Diego Padres for a surprisingly low return. As it turned out soon after, that was the best possible offer that could be had. There were fans who just didn't believe it, thinking that Arraez was highly valuable due to his batting titles.
It's true that Arraez is a great contact hitter, but his poor defense and lack of power severely limit his value. That's something that was seen as a significant issue by other teams, but for some reason was completely ignored by this obviously false narrative. The other part of the narrative is of course that Bendix should not have moved Arraez if the return was so low.
The latter does make some sense, however he's a free agent after next season and was clearly not an extension candidate. It's certainly possible that waiting and keeping him would've made sense, but with the season lost and his being a free agent after next season sealed his fate.
Too little time passed to truly evaluate Peter Bendix, but rest assured he's not trying to hurt the Miami Marlins.