local currentHealth = getCreatureHealth(cid)
local removeHealth = currentHealth - 1
doTargetCombatHealth(0, cid, COMBAT_PHYSICALDAMAGE, -removeHealth, -removeHealth, CONST_ME_NONE)
I don't understand what you want exactly. You want to remove full player's health to 1? Something like this?
LUA:local currentHealth = (getCreatureHealth(cid) - 1) doTargetCombatHealth(0, cid, COMBAT_PHYSICALDAMAGE, -currentHealth, -currentHealth, CONST_ME_NONE)