You should not drive a vehicle with tires of different tread depths. When tire treads are worn unevenly, it can pull the car to one side or the other. You will have a harder time controlling the vehicle. Additionally, tires with less tread will lose traction more quickly on wet roads, which can lead to hydroplaning or skidding.
Having different tire tread depths can also cause uneven wear on the tires. This can lead to premature tire failure and tread separation, which may lead to a crash.