After falling in debt to a crime family, a cocky mechanic is forced to strip stolen cars for an auto-garage, but when his love interest is killed in a hit-and-run caused by the family’s erratic nephew, he turns the family against itself to seek vengeance and escape the debt.

Great start. I like revenge stories and especially when there's something fresh about them.

>>a cocky mechanic

What's the intent behind cocky? A guy taking revenge indirectly doesn't sound cocky and he doesn't feel so ironic in that predicament. With the predicament he's in and the indirect plan, a significant flaw doesn't even feel necessary. Was it considered to go with a trait or talent that would shed light on how he would turn the family against itself? In other words, to differentiate this more from the first Punisher movie.

>>After falling in debt to a crime family,
>>is forced to strip stolen cars for an auto-garage,

These can be combined and shortened since the real hook starts when the love interest is killed.

>>to seek vengeance and escape the debt.

Escaping the debt is understood with the vengeance.

Does it pay specifying the main antag?

My two cents.

The most interesting part of this logline is the protagonist's plan to seek vengeance by turning the family against itself. I absolutely love that. Because of this, get rid of the debt subplot - it's unnecessary and not as interesting.