Hermit from Hell!!!

you get mad at a guy just cause he is hungry????  :-)

sounds like you got a teenager crab.  He eats like my 13 year old.   

I had one of those... Lets just say he is crabby heaven.

I've had pretty good luck with scarlets being pretty safe.  So do double check the ID.  That said there are always those individual specimens that just can't help themselves.  Doesn't matter what kind of hermits they are, the little guys compulsively check shells that are anywhere near the right size for them.  They will also be forced to hunt if they are not well fed. 

My plan:  try to only keep snails much larger or smaller than your hermits, think nassarius, nerite and mexican turbos.  The ceriths and astreas always seem to be the most picked on.  Also, target feed the hermits a couple times a week to make sure they are getting enough food that they don't start feeling desperate. 

In one of my picos, the two scarlet hermits are the only things that really need any feeding, so I pull them out a couple times a week and put them in a bowl with a 1/2" of tank water and a small dollop of zoomed hermit crab canned food.  Give them a couple hours to stuff themselves and then back to the tank they go.  Then the dish gets dumped and washed.  Water quality stays high, and they leave the snails alone.  If you are still having issues, your rogue specimen may need a new home, or if he really is destructive, you might consider making him into a crabsickle.