Deadly
Part of speech: adjective
Definition: lethal very accurate (of aiming with a bow, firearm, etc.) very boring excellent, awesome, cool
Part of speech: adverb
Definition: Fatally, mortally. In a way which suggests death.
Example sentence: History has shown that a government's redistribution of shrinking wealth, in preference to a private sector's creation of new sources of it, can prove more destructive than even the most deadly enemy.
Harmful
Part of speech: adjective
Definition: of a kind likely to be damaging; injurious
Example sentence: The law is an adroit mixture of customs that are beneficial to society, and could be followed even if no law existed, and others that are of advantage to a ruling minority, but harmful to the masses of men, and can be enforced on them only by terror.