After going through all of my mods, it turns out that The Aether mod lets players bypass bleed out by disconnecting when they are in the bleed out state.

Is is a known issue with FirstAid and Spice Of Life (all versions except Onion). Can you send me your mod list?

My (and my server's) modpack has been updated and has new mods. But my logs from my comment from a previous issue still shows the mods I had installed at the time this issue was created.

I have reported the issue to the aether team. I tested it myself with just PlayerRevive and The Aether installed and the issue is still there. Let's hope the issue can be fixed.

Actually that works! Thanks @bconlon1 for suggesting this solution (probably by far the easiest). New version with this fix is out.

You could likely solve this by setting the SubscribeEvent to a higher priority, if you want the kill behavior to be guaranteed. Let me know if that works.