torment vs pester

torment is a noun but pester is not a noun.

Word	Noun	Adjective	Verb	Adverb
torment	Yes	No	Yes	No
pester	No	No	Yes	No

As verbs, pester is a hyponym of torment; that is, pester is a word with a more specific, narrower meaning than torment:

Other hyponyms of torment include madden, hamstring, badger, beleaguer, bug, tease, oppress, persecute.

torment (noun)	pester (noun)
the act of harassing someone
a severe affliction
intense feelings of suffering; acute mental or physical pain
extreme mental distress
a feeling of intense annoyance caused by being tormented
unbearable physical pain

torment (verb)	pester (verb)
subject to torture	annoy persistently
torment emotionally or mentally
treat cruelly