An aging Vietnam Vet haunted by his past puts his war time skills to good use as he seeks revenge on the drug dealer who killed his daughter; along the way he takes out a couple of crooked cop.

Good concept, although it's been somewhat over-done ("Rolling Thunder" comes to mind). You'll need a "hook" that separates it from all of the other sound-alikes. Also, a bit too wordy for a proper logline, IMO:

"An aging Vietnam Vet, haunted by his daughter's murder, puts his killing skills to use as he seeks revenge on murderer and the crooked cops who covered it up."