Anti-oneshot

Anti-OneShot provides players with a last-chance survival mechanic against lethal attacks.

Main Effect (Anti-OneShot Protection)

When a player above the HP threshold receives a killing blow, the damage is intercepted. The player survives with a small HP remainder, gains brief invincibility and Absorption, and enters a 120-second out-of-combat cooldown.

Extreme Mode (Secondary Effect)

While the main effect is on cooldown (in worlds without keepInventory, or Hardcore), a second killing blow triggers an emergency backup — but applies a stacking max HP penalty (-20% per level, up to 2/3/4 levels by difficulty). The penalty degrades one level every 120 seconds, and is force-cleared when the main effect cooldown resets.

• HUD: cooldown timer and extreme buff level in the corner
• Screen flash: red vignette border on trigger
• Camera shake: brief impact shake on trigger
• Transparency: local player turns semi-transparent during immunity
• Sounds: distinct audio for main trigger / extreme trigger / cooldown end, all configurable

Config file: config/anti_oneshot.cfg. All parameters can be changed in-game via commands.

/antioneshot (/aos)
  config list                    — list all config keys
  config get <key>               — query a config value
  config set <key> <value>       — update a config value
  config reset <key|all>         — reset to default
  status [player]                — show cooldown/buff status
  reset <player|all>             — force reset cooldown
  clearbuff <player>             — remove extreme buff

Drop the JAR into your mods/ folder. Requires Forge 14.23.5.2847 for Minecraft 1.12.2.