Presume the tires match, and are both sound, right?

Were the old pads evenly worn when you removed them? That is, did it appear that the inboard or the outboard pad on the left side was less worn than the other three front pads?

Tie rod ends in good shape?

When you say that it pulls hard to the right, you mean that if you let go of the steering wheel it would spin to the right, correct? This as opposed to the car simply changing directions when you apply the brakes. The car can change directions if the rear axle shifts when the brakes are applied.

Have you verified that both back brakes are actuating?

Find a spot where traction is limited but even for all four wheels, like a smooth patch of dirt, and apply the brakes until the wheels skid. Check to see that both fronts and both rears start skidding at the same time.