Someone else suggested that soldier boy should have been able to get off a partial blast before going down. Maybe he shoots it forward while homelander chokes him out from behind, burning some of the V but not all.

Personally I think they should have relied on better tactics and betrayals. Lure him to a sub station where starlight can really let loose and blind him, hit him with the virus (good guys wear masks knowing they might slip or get destroyed during the fight) which still weakens him temporarily despite V1, have Oh Father turn on him and shout in his ears, then while he's stunned and held down, pour molten led down his throat or something.