Anti-Trust?

What if the government isn't interested in that?

Civil law suits.

That's going to be really hard when the court is stacked with those sympathetic to the conglomerate because it can buy unlimited political influence.

This is not the case when there's a multitude of smaller players that have a vested interest in maintaining a competitive marketplace, or where they're all boxed in by regulations so that investors don't get wild ideas about unlimited potential profits.