what can cause this car to be completely dead even after I charged the battery?

Hello, You may have a bad connection to the battery due to a bad battery cable, corrosion, bad terminal, or bad connection from the positive post to the power distribution box (underhood fuse box). Start small, check grounds, fuses, relays, and battery connections, then, if nothing works still, use a test light or multimeter to identify what actually has battery voltage, starting with the battery terminals. You may just have a bad battery also. Does the vehicle work when it is connected to jumper cables? (See our how to on properly jump-starting a car).