An archeologist’s family struggles to stay alive, after a failed expedition in the remote jungles of the Amazon awakens a supposed extinct, cannibalistic humanoid that terrorizes and hunts them, one by one.
So failure is what it takes to invoke vengeance by a humanoid cannibal? Sounds like some teachers whose tutelage I had to survive.
But seriously, the standard mytho-poetic formula is that daemonic forces arise to wreak revenge for failure to respect taboos, failure to avoid trespassing on sacred grounds, failure to respect sacred objects. I suggest that the definition of the expedition’s failure needs to be refocused and made more specific.
An inciting incident would give the story a starting point and add legitimacy to the creature’s vengeful tendencies.
After disrupting the tomb of an ancient beast an archaeologist must fight a cannibalistic humanoid to get his family safely out of the Amazon.
Hope this helps.