An unassuming immigrant unleashes his secret oriental power on the criminal cartel intent on corrupting his family.

I like the second of those two, but I would say Unassuming immigrant instead of tiny.

Thanks Richiev .I agree it needs a little more.

How about this:

An unassuming immigrant unleashes his secret oriental power on the criminal cartel intent on luring his teenage children into their cabal of drugs, extortion and prostitution.

Or, with a little but more info infused:

When a dangerous cartel lure an immigrant's son and daughter into their underworld of drugs and prostitution, Tiny turns his back on the pledge made to his dead wife and unleashes his ancient oriental power.

Everything is there.

I would try personalizing it a little bit; instead of saying "corrupting his family," how are they corrupting his family?

But this logline at most just needs tweaking not a major re-write.

"When a criminal cartel lures his naive son into their organization, an unassuming immigrant unleashes his secret oriental powers to get him out."