unfortunately; unluckily; regrettably
Used to express that something bad or regrettable happened, often at the beginning of a sentence or clause.
不幸にも、その日は大雨だった。
Unfortunately, it rained heavily that day.
彼は不幸にも事故で亡くなった。
He regrettably died in an accident.
あいにく is a casual, everyday way to say something happened unluckily, whereas 不幸にも is more formal and often used in written or narrative contexts.
幸いにも means 'fortunately', describing a lucky outcome, directly opposite to the unlucky sense of 不幸にも.
Formed from 不幸 (misfortune) + に (adverbial particle) + も (inclusive particle), literally 'even in misfortune' or 'as a misfortune'.