“Why not just unleash it and be done with it?”

Because when those who choose to do evil (maybe because of how they experience the ‘rewards’ of power and control), eventually want or need even more power and control, they need to be sure that a “supply “ remains available so as not to spoil their pleasure through with total and instantaneous obliteration.

In answer to your initial question, it seems apparent, imo, that cv -19 and everything related to using bioweapons, in general, eventually cause ever increasing levels of harm to targeted populations through the endless use of fear, vaccinations, boosters, lockdowns, newer technologies, tyranny, isolation, societal divisions, death, transhumanist agendas, depopulation, etc. if the bioweaponry is not recognized as such by the population before it is too late.