What will happen if we kill all the organisms in one trophic level?

In a food chain, organism at each trophic level is responsible for flow of energy. If we kill all the organisms in one trophic level this flow of energy would stop, creating an imbalance in the ecosystem. It will result in increase in population of organisms at previous trophic level and decrease in population of organisms at next trophic level. If all primary consumers die, the number of plants will increase immensely and the secondary consumers will die due shortage of food.

For example, in the given food chain,

Plants → Deer → Lion

if all deer and other herbivores die, the number of plants will increase and animals like lion will die due to starvation as there will be no herbivores left.