All these even after Michael confided in Fredo in Havana and Fredo assured Michael, Michael could trust! Fredo and Fredo even offered to help! Michael

Quote
Michael: Can I trust you with something, Fredo?
Fredo: Of course, Mike
Michael: Later on in the evening we're all invited to the Presidential Palace reception, to bring in the New Year After it's over - they're gonna take me home in a military car -- alone -- for my protection Before I reach my hotel, I'll be assassinated
Fredo: Who?
Michael: Roth -- It was Roth who tried to kill me in my home It was Roth all along He acts like I'm his son -- his successor -- but he thinks he's gonna live forever -- and he wants me out
Fredo: How can I help?

It seems to me, Fredo is even more cunning, devious and ruthless than Vito and Michael put together!
Vito may have picked the wrong son! for Donship

The way Fredo, among others -
  • denied knowing Roth and/or Ola
  • sat through the brothers having drinks, hiding his true feelings without raising any suspicions
  • pretending he has never been to Havana before -- how do you say "banana daiquiri"?
  • absorbing the shock of Michael knowing it was Roth who tried to kill Michael in his home – without batting an eyelid
  • Fredo's demeanour certainly fooled Michael

Wow! And the Oscar goes to....