And yes to padel, we can smash on a smash. It's even a pretty common blow to the padel.
Just do not support his smash enough and the opponents defend well to get a smash against.
The defender gets closer to the net and waits for the ball to come back from behind and then against the smasher. Here we go for a small picture:
So you say, a possible counter-smash? And yes, it is possible… In reality at padel, we can do anything ad infinitum because the ball can always come back.