I think you are asking are there Chinese characters whose Pinyin symbols start with the letter 'o', there is only a few, and all of them are exclamations, such as 哦, 噢 and 喔. So, there isn't any adjectives among these characters.
Complimentary adjectives that start with the letter a:ableaccessibleadorableagreeableamazingangelicappreciativeartisticastuteathleticattractiveawesome
Some adjectives that start with the letters BLA are:blackblamelessblanchedblandblaringblatant
Good
· xyloid
Some adjectives that start with WR are:wraparoundwrathfulwreathedwreckedwrenchedwretchedwrigglywrinkledwrittenwrithingwrongwry
aggressive
motivating, moving
· entertaining
· klutzy
· witty
· authoritative · articulate
Outstanding, optimistic, outgoing and observant are positive adjectives.