dead fish make good plant fertilizer. can't say I've ever had a "monster" pass on me but tetras, and other such. dig a hole.. drop dead fish in.. cover.. never had a problem having 'em dug up. otherwise frozen 'n tossed out on trash day in the winter.
monster fish , havent had to yet but all other fish go to neighborhood cats when our blood parrots died, i threw it out in the lawn and i went back inside for something and came back out and there goes a black cat with a big orange ball in his mouth.
I wrap mine in a plastic shopping bag and into the freezer it goes until right before I take the trash out on garbage day. this helps to avoid the dreaded dead fish smell.