I started with 4 neons and 1 male betta in a 5G tank. After about 2
months I noticed that only 3 neons were left. About a month later only
2 left. He seems more and more agressive towards them as he chases them
around the tank. It seems as if it is a food issue and he chases them
from where the are feeding on food at the bottom of the tank. I try to
feed him more, but he goes about looking for food and chasing the
neons.

Not only are 2 neons missing, I cannot find any remnants of them at
all. Is it possible that he ate the entire neon?