Tom generally is, to quote Tony Soprano, like Gary Cooper. The strong silent type. He keeps his feelings on things unspoken, generally.

That said, we see him observe Fredo trying to show Anthony how to fish in a brief moment. He also doesn't seem to speak of Fredo with either warmth or rancor after Cuba - more just giving a matter of fact report that Fredo is in hiding in New York. He doesn't suggest ways to get at him, nor does he try to sue for clemency for him.

But we see that he has a growing disgust for Michael's obsession with vengeance as he lets his feelings slip that Michael doesn't need to kill EVERYONE to make a point - which for Tom is a rare show of emotions. Or when Frankie says to Tom (in private) that the Corleone Family was like the Roman Empire, he replies with both wistfulness and bitterness "It was once."

Tom only seems to not leave Michael's side at the end of II out of fear of reprisal - be it being murdered for being a liability, or for Michael to spitefully ruin his marriage by exposing his affair (Say Tom DID leave - can you really put it past Michael to expose him and ruin him legally and personally?)

That all being said, what do you think Tom felt about Fredo being executed? Tom is no Connie - he is too smart, and not capable of enough self delusion to make himself believe the drowning story. He also knows the depth of Michael's ocean of ice, having experienced it to a degree himself.

So, what do you think were his feelings on it all? Do you think he cared? Or, was it to quote Cromwell upon viewing the corpse of the recently executed King Charles I a "cruel necessity" and nothing more?