What is disproportional reaction?

Answer 1

Disproportionate means unequal.

In physics if you drop a stone into a pool and all the water immediately splashes out of the pool what you have is a reaction that does not match the energy that went into it.

A disproportionate reaction can also be different.

In some countries people are killed for less reason than in other countries.

Or understated.

The current building code may leave a building unable to cope with a big earth quake, but it may deal fine with minor ones. While those funding the build may think that the architect has a disproportionate account of what is needed, the residents may feel differently and the building may become difficult to rent or sell. Of course if it is more than reasonably secure it may too expensive for enough people to buy an apartment in it.

Disproportionate reactions can be too much or too little. And can be governed by many considerations, like politics, funding, weather, physics...