oblivious and insensible
obloquy and detraction [obloquy = abusive language]
obnoxious and odious
obscure and enigmatical
obsequies and panegyrics [obsequies = funeral rite]
[panegyrics = elaborate praise]
obsequious and conciliating [obsequious = servile compliance; fawning]
observations and reflections
obstacles and disasters
obstinate and stupid
obstreperous and noisy [obstreperous = stubbornly defiant]
obtrusive and vulgar
obtuse and imbecile
obvious and palpable
occasional and contingent
occult and hidden
occupations and habits
odd and dismal
odious and oppressive
offensive and aggressive
official and authoritative
oily and servile
old and decrepit
ominous and untrustworthy
omnivorous and sordid
oneness and unity
onerous and perplexing
open and inviting
opinions and hypotheses
opportunism and inconsistency
opposite and discordant
oppressed and sullen
optimistic and reassuring
opulence and magnitude
oracular and occult [oracular = solemnly prophetic; obscure]
order and uniformity
organic and rational
organization and system
origin and discovery
original and attractive
ornate and variegated
ostensible and explicit
ostentatiousness and gaiety
outlines and appearances
outrageous and scandalous
overburdened and confused
overcome and vanquish
overstep and contravene
overt and unmistakable
overwearied and outworn