ok here's an idea,
set in a place where a man eating animal is native to (species/location irrelevant), movie starts with a hunter/group of hunters killing the creature. As he/she/they do the rounds and dismantle all the natural traps etc they had laid, he/she/they find a trail of strange green goop and follow it to track down a dying/dead predator and pit a few rounds in it to be sure.
Now, later on some mysterious "government agents" take away the body and try to cover up the incident, feeding the character/s a bs cover story and disappear. The character/s friends and family start to disappear throughout the course of the movie and no mayter what they do or try nothing can stop the people closest to him/her/them getting butchered.
Let's say the few who weren't armed to defend themselves get scalped alive and left mutilated, eventually when the main character/s are just about to give up the "government agents" return and fill in the details on the enraged predator exacting revenge for it's fallen comrade, an a team is set up to take it down, which the main character/s are needed to be used as bait.
All this leads to some type of showdown etc etc