- He could have become the President if he had contested the election.
- I was so angry I could have killed him.
- I could have married her if I had wanted to.
- She could have won the race if she had run a bit faster.
This structure can also be used to criticize people for not doing things.
- You could have asked me before using my computer.
- You could have finished that project before starting another.
- You could have locked the door before going out.
- He could have consulted his doctor before taking that drug.