~아/어/여 버리다 = Action ends completely, usually with a strong feeling either of being happy or sad that it’s finished

어제 산 핸드폰을 잃어 버렸어요 = I lost the cell phone I bought yesterday.
안 좋은 일은 다 잊어 버렸어요 = I’ve forgotten all the bad things (I am done with them.)
빨리 끝내 버리세요 = Finish it quickly and be done with it
벌써 다 말해 버렸어요 = I’ve already told them everything (It’s done. It’s over.)
10분 더 기다려도 안 오면 저 혼자 가 버릴 거예요 = If I wait for 10 more minutes (and) you don’t come, I will just go by myself.
어제 쓴 글이 마음에 안 들어서 다 지워 버렸어요 = I didn’t like what I wrote yesterday, so I’ve erased it all.
효진 씨한테 기다려 달라고 했는데, 그냥 가 버렸어요 = I asked Hyojin to wait, but she just left.
컴퓨터가 멈춰 버렸어요 = My computer has stopped. (And it’s causing me trouble.)
시작한 김에 오늘 다 끝내 버리는 거 어때요? = Now that we’ve started it, why don’t we just get it all done today?
영화가 벌써 시작해 버렸어요 = Oh, no! The movie has already begun!