Modals to express criticism: CAN, COULD, MIGHT, SHOULD

Present and future

Can, could, might and should/shouldn't + infinitive are used to express criticism or disapproval with reference to present or future time:

You can be really annoying, you know! 
You shouldn't be sitting here just doing nothing!
You might be more polite.
George could really help you!

Past

Could, might and should/shouldn't + perfect infinitive are used to express criticism or disapproval with reference to past time:

I should have booked a table in advance.
Of course, you feel sick. You shouldn't have eaten so much chocolate.
You might have told me you weren't coming!
George could really have helped you!