Which one is the worst ever transfer window in football clubs history?

PSG 2021/22

Lazio 2020/21

Bayern Munich 2020/21

AC Milan 2017/18

Manchester United 2017/18

Tottenham 2013/14

Barcelona 2021/22

 Manchester City 2015/16

Chelsea 2017/18

Manchester City 2012/13

Arsenal 2015/16

Chelsea 2022/23

 Liverpool 2014/15