most poisonous

ADJECTIVE

harmful

Synonyms

WEAK

bad baleful baneful corrupt corruptive dangerous deadly deleterious destructive detrimental evil fatal hurtful infective lethal malicious malignant mephitic miasmatic morbid mortal nocuous noisome noxious peccant pernicious pestiferous pestilential septic toxic toxicant toxiferous venomous vicious viperous virulent

Antonyms

WEAK

aiding antidotal assisting curing healing helpful

ADJECTIVE

harmful

Synonyms

STRONGEST

dangerous deadly destructive fatal lethal noxious pernicious toxic venomous vicious virulent

WEAK

bad baleful baneful corrupt corruptive deleterious detrimental evil hurtful infective malicious malignant mephitic miasmatic morbid mortal nocuous noisome peccant pestiferous pestilential poison septic toxicant toxiferous viperous

Antonyms

STRONGEST

gentle good harmless healthful healthy helpful kind life-giving nice nonpoisonous wholesome

WEAK

benevolent non-toxic

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

The death cap is the world’s most poisonous mushroom, responsible for 90% of mushroom-related fatalities.

From Los Angeles Times • Jan. 16, 2026

Stonecipher was the first in a line of future Boeing CEOs influenced by General Electric’s Jack Welch, one of the most poisonous individuals in American business since the robber barons.

From Seattle Times • May 13, 2022

Although not the world's most poisonous snake, the saw-scaled viper is quick to bite when it feels threatened.

From BBC • Oct. 19, 2021

But to detractors, he was less a refined and perceptive authority on art than a mean-spirited curmudgeon — “the most poisonous pen on Broadway,” as Time magazine dubbed him in 1973.

From Washington Post • Nov. 25, 2019

“Jellyfish are really mysterious to me. The most poisonous one in the world is the size of a gnat or something.”

From "Ivy Aberdeen’s Letter to the World" by Ashley Herring Blake