You can use unfortunately to introduce or refer to a statement when you consider that it is sad or disappointing, or when you want to express regret.
regrettably
Unfortunately, my time is limited.
遗憾的是,我的时间有限。
Unfortunately for him, his title brought obligations as well as privileges.
遗憾的是,他的头衔既带来了特权也带来了义务。
The enclosed photograph is unfortunately not good enough to reproduce.
很遗憾,附寄的照片不够清晰,无法复制。