Synonyms: fatal, lethal, deadly, mortal, terminal
fatal: causing people to die
Example: There were three fatal accidents on this road last year.
lethal: dangerous and able to kill someone
Example: a lethal dose of painkillers
Example: a lethal mixture of drugs and alcohol
Example: Being out in the sun too long can be lethal.
deadly: likely to cause people to die
Example: The terrorists turned the car into a deadly weapon.
mortal: referring to injury serious enough to cause someone to die
Example: a mortal wound
terminal: referring to the last period of a serious illness that will lead to death
Example: The condition is terminal