A young martial artist must find his uncle and request his help in fighting his father, a martial arts master who is determined to kill him.
A young man must persuade a legendary martial arts master to train him to fight another martial arts master who has vowed to kill him — his father.
The logline as posted has the basis elements, but I thought it could be spiced up. First of all, I presume that the uncle is a martial arts master in his own right — why else would the young man seek him out? If so, then it seems to me for the purpose of the logline ( which often compels tradeoffs between economy of words and completeness of conceptualization) that the reputation of the uncle would be a more of a need-to-know element than the relationship. (Although, of course, it could still be part of the story.)
And, it seems seems to me that finding and asking the master would only be a first step. That the core of the 2nd Act, the most dramatically interesting aspect , would not be the finding and asking but the training. ( “The Matrix”, “Karate Kid”, “Rocky” — any number of movies come to mind with plots building to a High Noon showdown between a protagonist in desperate need of a skill upgrade against a dangerous foe.)
Finally, my version delivers the hook where it profits from the most emphasis, the end, as a punchline.