The phrase "achieved unexpectedly" is correct and usable in written English.
It can be used to describe a situation where a goal or result was reached without prior anticipation or planning.
Example: "The team achieved unexpectedly high sales figures this quarter, surpassing all projections."
Alternatives: "accomplished unexpectedly" or "attained unexpectedly."
That example of verbatim theatre, using taped interviews of local residents who lived near the rented room of the convicted killer (now serving a life sentence), related the crimes' reverberations through the community as well as the healing process achieved, perhaps unexpectedly, through flower competitions.
Paul achieved an unexpectedly strong second-place result in New Hampshire.
Taylor received £710,000 as a "transaction bonus" on achieving the unexpectedly high sale price, another £509,000 for loss of office when he left GMG on 30 June following the sale, as well as more than £100,000 in salary and pension payments.
We were achieving an unexpectedly hot and complete ("clean," in firefighter parlance) burn, given the conditions.
For example, there were many items located in the 2nd quadrant (hard items that were unexpectedly achieved) and the 4th quadrant (easy items that were unexpectedly not achieved).
Though Sue originally thought her case unique, she has found other accounts of people who have unexpectedly achieved stereo vision through vision therapy….
Though Sue originally thought her own case unique, she has found, on the Internet, accounts by a number of other people with strabismus and related problems who have unexpectedly achieved stereo vision through vision therapy.
Ignored by the outside world, the Syrian Kurds unexpectedly achieved international notoriety when they successfully defended their city of Kobani against IS assault in a 134-day-long siege that ended earlier this year.
With a typically enigmatic installation that won high honors at the most recent Venice Biennale, the expatriate Conceptual artist Cai Guo-Qiang has unexpectedly achieved every artist's dream: he has provoked a debate, long overdue, in his officially stifled native country about the meaning of art, originality and the avant-garde.
