A disgraced winemaker sets out to exact revenge on the farmer he thinks sold him poisoned grapes.

As nicolesigaud has pointed out, there is no inciting incident in this version. Add the inciting inciting incident here and it's a step in the right direction.

The inciting incident from your previous attempt: "When his celebrity drinkers die" played for comedy value could work really nicely. The only thing I would suggest is to up the stakes:

When he's accused of manslaughter after an A-list celebrity dies, a disgraced winemaker plots his revenge on the farmer he believes sold him poisoned grapes.

I like the addition of the police aspect because it adds a subplot and additional antagonistic elements that could be fun exploring. It also increases the motivation for the protagonist - not only is he trying to clear his name, he's trying to stay out of jail.

Out of curiosity, did the farmer sell him poisoned grapes? If so, why?

I did not see the inciting incident, meaning what triggered his revenge. I think parts of the first version could be used with this one to improve it.