Well, bone pulverization is a real risk for your character.
There’s a simple solution, but first, let’s talk about strength, and what
that means when your character is inhumanly strong.
Even without a superpower, your body is strong enough to tear itself apart.
The classic examples are improperly tensed punches, which can do all kinds of
horrible things to your hands, and improperly lifting heavy objects, which can
tear up your back.
Personal experience has seen both of us do pretty horrific things to our own
bodies without needing super strength.
Adding superhuman strength to the mix just exacerbates this. Your character
can lift a statue, but it will do horrific things to the weakest structural
point on their body. This is not a function of lacking the strength to lift it;
it’s the result of their spine being strained beyond its breaking point.
One really good example is, if you have a character with cybernetic arms,
you need to anchor those to their spine, reinforce that and their legs, or
they’ll be able to rip their own arms off by picking up a car.
If you can throw a punch with sufficient force to send a midsize sedan
flying, you will break every bone in your hand, (and possibly shatter
your arm.) Even using proper techniques. Your body simply isn’t built to handle
that kind of force. Also, it’s not going to send the car flying, I’ll come back
to that in a minute.
The simple solution is to also make your character inhumanly resilient to
damage. This has some other considerations. The same resilience that allows
them to actually punch someone at full force will protect them (to some extent)
from the people they’re fighting.
This isn’t the only possible solution. For example: a character who can
reassemble their body on the spot, no matter how mangled it becomes could use
super-strength, with the understanding that they’d need to spend a few minutes
putting their arm back together after they reduced their foe to goulash.
Without any additional powers, super strength becomes a very tricky thing to
use. Your character could still have it, but need to be very careful with how
they use it, and pull their punches. Not because they’re concerned about their
opponent’s well being, but because they don’t want to destroy their own body.
That said, a character with super strength can literally tear their foes to pieces, if they choose to. Using the
statue example, you’re already talking about a character that exceeds the
tolerances of the human body to a comedic degree.
So, the simple answer to, “how much damage” is probably, “chunky salsa.”
I mentioned that the car wouldn’t go flying a minute ago, so let’s explain
the problem. Your average car weighs around 3000 to 4000 lbs. Your average super
hero weighs between 100 and 250 lbs. When your character tries to punch that
car, the force will go both ways, and the relative masses become far more
important than how strong your character is to determining who will win. With
proper bracing, they can probably kick the car a few feet, but without
something to brace against that extra strength doesn’t translate into airtime
when you’re tossing around improbably large objects.
This doesn’t mean your character would throw a punch at a car, and go flying
in the opposite direction (they’re far more likely to find their hand embedded halfway into it, because the force has to go somewhere), but it does mean they’re not going to be
able to use a ’57 Chevy as an improvised club.
Again, this is something that characters who can flat out violate the laws
of physics can get away with. A character who can rechannel kinetic energy, or lock
themselves into their environment, can start to fundamentally mess with how
mass behaves. They’re not a 150lb guy grabbing a car; they are a 150lb guy who is
functionally fused into the city street, tossing around a car. Also a character
who can alter their own effective mass on the fly could lead to some really absurd
Berserk like combat sequences.
Alternately, you can have characters that pick up the car, try to throw it,
and send themselves flying in the opposite direction. It’s not exactly realistic, but there’s comedic merit
to the approach.
So, the basic advice for this is, study some basic physics, and have fun
with the absolutely insane things you never thought of before.