Again there really is zero evidence that shows Fredo wanted to kill him
Yes, If Ola had flat-out asked Fredo to help in the murder of his brother, Fredo would have said no. So, Ola played him--Michael was being tough on negotiations, they needed information, bla-bla-bla. But, Fredo just closed his eyes,,ears and mind to what was going to happen when Ola told him to
open the drapes--especially since he was promised "there'd be something in it for me.":