I enjoy my tiger barbs, seven adults and about 28 youths divided amongst two tanks.
Historically, before I knew better, we had one barb in with platys, guppies and neon tetras. It was aggressive for a couple of weeks then just chased its reflection for hours not bothering a soul. A later batch contain a mean little barb (see "Stab" in another thread) who attacked the other barbs, left the platys alone (only fish left), and loved to tug on the tail of the pleco about five times his size.
A large group of youth (over 30) would take nips at a cory catfish and occasionally the pleco.
I would definitely recommend keeping a group of six or more to dissipate the aggression. I think the group pacified when I added some plantlife (a couple spades and some grass) for them to play in.