1) a person who is addicted to something harmful (addict)
2) to influence or change (the condition of something) especially in a harmful way (affect)
3) a substance in the blood which destroys harmful bacteria etc (antibody)
4) harmful or unhelpful action (disservice)
5) any strong or harmful drug (e.g. opium); a stupid person (dope)
6) harmful competition between colleagues or rivals (especially in commerce or industry) (infighting)
7) harmful to life (malignant)
8) (of such metals as 'uranium') having atoms that break up and, in so doing, send out electrically charged particles that can be harmful (radioactive)
9) any one of a group of long, legless reptiles, some of which are poisonous; an insincere, harmful person who pretends to be a friend (snake)
10) of suicide; very harmful (suicidal)
disastrous
disastrous; tragic
causing, likely to cause, death
causing end of life
causing destruction; fond of, in the habit of, destroying
injurious, devastating
causing disaster
detrimental, devastating
very wicked, bad; likely to cause trouble
sinful, immoral
severe
severe, painful; serious
causing, likely to cause, injury
hurtful
causing, able to cause, death
deadly
filled with lice
very bad
filled with, engaged in, mischief
devilish, wicked
harmful
deadly, injurious
extremely harmful, causing distress
bad, hurtful
causing ruin
disastrous, devastating
suggesting evil or the likelihood of bad luck
nasty, menacing
poisonous (the usual word)
poisonous
(of food) not good for one's health; harmful
unhealthful
(of a person) strong; (of ill-feeling, hatred) very strong; (of words etc) full hatred; (of a disease etc) very dangerous
poisonous, lethal
