Stop using counterforces to calculate problems.
This is a warning I cannot stress enough. If you want
to calculate problems, choose the one object you are
interested in and draw which forces are active on this object.
In your case this means
- the body with 100 kg mass. Gravitation forces the body down.
Now you can calculate if the body crushes thrcough the floor
or how compressed the body will be if you know its elastic
modulus, what force is necessary to overcome friction and so on.
- the floor. It is compressed by a body of 100 kg mass. So you
can calculate the pressure if you know how much surface area the body
has or you can calculate the bending of the floor caused by the mass
and so on.
As you already found out, you only get garbage solutions out of it because you hide which problem you are actually solving: Are you trying to solve the movement of the body or the movement of the floor? The lifting force you are using does not act on both body and floor and therefore you get confused by nonsensical answers. What you can do is solving each problem from every available viewpoint (body/floor) to see how the forces interact, but never mix forces with counterforces for solutions.
I see that the problem is still not clear.
Let's imagine the 100 kg body is a human. Let's take two of them, one of him is put on the ISS, the other one stays on earth. Both are staying still.
If the drawing would be fine, then it is no difference between both bodies: Both have balanced forces, the one on the ISS having 0 N, the other one having 100 daN (~ 1 kg) in opposite directions, each canceling the other out.
So they should feel no difference if the drawing is right? But there is a difference, on Earth we feel pulled down. Our bones are compressed. The floor on which we are standing is bent and is depressed around our feet.
If the forces are really canceled out, then the originator of the question should be right: Applying 1 daN upward should move the body upward. But it does not: Mysteriously the "counter force" is now decreased by 1 daN. What causes exactly the strange "counter force"? Hm, the force is caused by the compressed molecules under our feet. Why are the molecules are compressed? Because the weight of our body...
The real problem is that the drawing shows the forces as two arrows, two separate entities when in fact for Earth only one is really active, gravitation. This single active (!) force cause all the effects we are observing, all things like bone compression and floor depression are simply reactive forces in response and do not exist independently from the main force. For this reason we should not include "counter forces" in our drawings and calculations as separate entities. It causes the following well observed paradoxons:
Unmoveable or freely moveable objects: If there is always a counterforce to a force, things could never move. Or, if counterforce is always equal to a force, things are always balanced and could be moved with ease (see above).
Counterforce chaining: Human does not move, human pushes floor down, floor pushes human up. Floor does not move, floor pushes human up, so floor itself must push down. House does not move, floor pushes down, so house must push up. And so on. It is not exactly wrong, but completely confounding and more or less superfluous.