If the Russians really wanted to kill Soldier Boy, couldn't they just drown him? No amount of super powers are going to save your body from a lack of oxygen.
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The meta side of me is thinking the same thing, seeing as they just got approved for season 4 and probably don't want to lose their star actor.
Though they might try to do something else like steal Homelander's powers away but keep him alive and suffer through Soldier Boy's rule at the top now. Probably going to do something more with Soldier Boy as they've been building him up this entire season with no very much screen time.