Need more advice about my Convicts

[ShyGecko]

I seriously don't think it's just a pecking order being established anymore. The aggressive one has picked on the passive one so much, that his/her fins are all chewed up, and a bunch of scales are missing or ripped to shreds. The poor thing can just sit up in the corner of the tank, hiding behind the heater, or shoves itself into the plants, facing down at the bottom of the tank, looking pretty much dead. I have to actually poke at it to get the poor thing to move. What should I do? Is it a lost cause? Should I take the aggressive one back to the lfs and try to get one that isn't as aggressive, or do you think it's not worth the effort...that the passive one will be this way with every tankmate? I feel so terrible for the little guy/girl. He/she looks completely exhausted. The aggressive one torments him non-stop, until he can't find him...then as soon as he does find him he's right back at it again.

HELP!!

btw...I've never had convicts before, so this is all new to me...