자업자득이 · 자업자득을 (often 자업자득이에요)
you reap what you sow; getting what you deserve
Example
공부를 안 했으니 시험에 떨어진 건 자업자득이에요.
You didn't study, so failing the test is your own doing.
Word parts
자 self+업 deed+자 self+득 obtain
Literally 'your own deeds, your own gain'—karma comes back to you.
Good to know
Sounds blunt and judgmental; be careful saying it directly to someone.