A 23 to 25 foot , 1 to 2 foot wide Anaconda has less to fear. Their massive bulk, thickness, reflex or defensive action strategy and size prevents them from getting hunted.
A large 25 foot Green Anaconda hiding in stealth under the floating forest is impossible to prey upon by any animal.
However Jaguars, Black Caimans, Orinoco Crocodiles are capable of preying on small and medium sized Anacondas. Anaconda weakness being they are slow and sluggish in land but once in water they are difficult to tackle.
Black Caiman is the only known massive reptile which is capable of fighting head to head with a massive female Green Anaconda.
Cannibalism is also documented amoung Green Anacondas with larger ones especially females eating smaller males after mating. So Cannibalism is not an alien behavior amoung Anacondas.
Some Amazonian tribes are not known to eat Anaconda meat