I've noticed that my tiger barbs are naturally more aggressive. They were really bad when I just had 2, but now that I have 5 they are better. I would think that they would sometimes pick another fish to death, but I'd never had it happen so I can't say for sure. I have a semi-aggressive tank and I have my tigers with red-eye tetras, guppy/molly crosses, a blind cave fish and cories. Everyone seems to do really well, although the tigers tend to pick on my apple snails
Also, my tank is fairly heavily planted so there's places for the others to hide if they need to.