What exactly did fredo do to betray Michael?

Fredo Corleone betrayed his brother Michael by conspiring with rival mobsters, particularly by collaborating with Johnny Ola and Hyman Roth in a plot to undermine Michael's power and control over the Corleone family. This betrayal culminated in a failed assassination attempt on Michael's life during a crucial moment in the family's history. Fredo's actions were driven by feelings of inadequacy and a desire for respect, but they ultimately led to a deep rift between him and Michael, culminating in Michael's heartbreaking decision to have Fredo killed.