Past modals of regret (skulle have, burde have)

To express regrets and missed opportunities in Danish, use a formula that closely mirrors English:

[Past Modal] + have + [Past Participle]

Skulle have and Burde have

Use skulle have ("should have") and burde have ("ought to have") for unfulfilled obligations and bad decisions.

I should have thought the plan through.
Jeg skulle have gennemtænkt planen.
Ought we to have thought it through?
Burde vi have gennemtænkt det?
She should have listened to her gut feeling.
Hun skulle have lyttet til sin mavefornemmelse.

Kunne have

To express a missed possibility (what someone "could have" done), use kunne have.

He could have trusted his instinct.
Han kunne have stolet på sit instinkt.
No one could have foreseen the outcome.
Ingen kunne have forudset udfaldet.

Negation

Place ikke immediately after the modal verb in a main clause.

You ought not to have ignored your gut feeling.
Du burde ikke have ignoreret din mavefornemmelse.
They should not have bet the money on something so risky.
De skulle ikke have satset pengene på noget så risikabelt.

Hindsight

When discussing regrets, bagklog (literally "backward-wise") is the perfect adjective for having 20/20 hindsight.

wise after the event
bagklog
We should have known it, but it is easy to be wise after the fact.
Vi skulle have vidst det, men det er let at være bagklog.