Frozen Terror and Light Zombie bosses are 950K HP so same HP, and the same kind of plugins
I compared both plugins. They handle damage the same way: both set var_health directly and use Ham TakeDamage for rewards and blood. Nothing in the Executioner code subtracts HP or multiplies damage on its own. Damage comes from outside the boss plugin, so the difference is in how the fights play out.
Why the two fights likely differ
Light Zombie spends a lot of time unhittable. His intro cutscene lasts about 20 seconds or more. He goes invisible (alpha 0) for around 12 seconds at a time, and he throws bombs and does crazy and nuke phases from range. Your players lose a big share of the fight to this.
Executioner is always visible and always walks straight into melee range. Every player can shoot him continuously, and splash weapons like grenades and rockets hit him all the time. Rage also doesn’t add any extra HP.
For a test i increased Teddy HP to 2.000.000 now so let me know if it still dies quickly