Generally, for obvious reasons, any pathogen that is extremely virulent will not also be extremely contagious. There are billions of years of cumulative evolutionary pressures against the existence of any such pathogen, and that result will be deeply encoded into all lifeforms.
Furthermore, it would be suicidal for any regime to vehemently seek to create such a pathogen. Bioweapons are intended to be delivered to specific target areas, except in the science fiction wherein immunity from a bioweapon that is both extremely virulent and extremely contagious can be reliably delivered to one’s own population and soldiers.
In my view, if anything COVID is close to being a bioweapon, it is the military capacity to massively, and repeatedly, rollout individual injections, which are physical vectors for whichever substances the regime wishes to selectively inject into chosen populations, while imposing complete compliance down to one’s own body, under the cover of protecting public health.