When a depressed office worker learns that his estranged, Chinese mob-boss father has been murdered, he must return home to avenge him!!

There's no need for the exclamation points, and "When" is usually not a great start for loglines. Also, I find myself asking the question "So what?"

I can't establish the mood, is it an hard boiled action movie or a comedy? As a comedy, It's better (a clerk who mess with the chinese mafia).
When a precarious chinese dishwasher learns that his estranged mob-boss father has been murdered, the mob rules force him to seek revenge.

This is a thin plot that reminds me of those Jacky Chan chop-socky movies that Shaw Brothers churned out every week in the 1960s. Does he need to be Chinese? As Nir Shelter says, it needs an antagonist and some stakes. Does he need to defeat a rival mob boss to inherit his father's evil empire? (Whoops, that's The Godfather) Does he need to stand up for himself because the rival mob want to kill him?