I had 2 sessions of Brazilian laser hair removal and now I regret it, the hair is almost all gone. Would the hair grow back?

A large percentage of the hair will grow back however, the area may have some thinning since not all of the hair follicles were in the growth phase at the time of your two treatments.

Much will depend on how effectively your first two laser treatments were.  Assuming they were at an appropriate fluence and that the treatments were performed about 2-4 months apart, you should have decreased you overall dark hair density by about 60-70%.  Typically 3-4 well performed treatments, will reduce the dark hair by more than 90% and the 10% that remain (assuming they had been treated but returned) will be finer than typical pubic hair.  If you don't do anything for at least 6months, you should be able to see how much hair actually is left.  It may be patchy at first but may even out a bit over time as the phases of hair growth flow into each other.  If you don't like how that looks you may want to complete your treatments.  Hope this helps a bit.