So who did the worst single acting job in the first 10 films.

[enterprisecvn65]

Decker in TMP. Just something about his all-American Apple-pie, self-righteous Goody two shoes...ugh. On second thought, maybe this is more of a personal vendetta, and hasn't much to do with his acting.

I actually thought he did a good job playing Decker. I will admit though that Stephen Collins' personal actions have made a lot harder to appreciate his acting talent in the films.
I've been guilty of laughing at it and making jokes, even though I know it's not something nice to do, it's sad that the whole phrase "Decker unit" has taken on the connotation it has because of his actions.

 

[Richard Baker]

Caithlin Dar was fine with me and the least of TFF's problems, really. I got the impression that she used her beauty and feminine wiles to get as far in Romulan politics as she could, but her foolish optimism put her government off, so they were glad to send her off to some loser posting like Paradise City to spin her wheels

The novelisation says she is part human, which might be another explanation for why she is sent to such a shabby post, and why she wears the ear protectors (to hide her "deformity").

http://www.ex-astris-scientia.org/inconsistencies/romulan_evolution.htm

And I always thought it was because her erectile hair style made her co-workers 'uncomfortable'...

For worst acting I wound go with Hardy as well. If he was supposed to be a younger Picard with the only differences being upbringing I simply do not see it. He just glowers and thunders around like a student in a high school play told to 'be evil'.

 

[eyeresist]

I think Hardy's Shinzon is the one that did the most to bring down a film. Never did I feel he was supposed to be Picard's doppelgänger--never did the personal animosity he had for Picard come to life.

You must have watched a different movie to the one I watched. The scene in the ready room was great.

 

[USS KG5]

Compare this to "The Godfather"...

Be fair buddy, NONE of the Trek films bears comparison with the first two Godfather films.

Don't get me wrong BTW, I get your point, but the rise and fall of Michael Corleone is one of THE great cinema stories.