Or was it a reasonable mistake, something that can justly be called an accident that few to none would have foreseen?
If it's the latter, how's this?
Nail the UN for the deaths, misery, and suffering. Have a proposed payment schedule worked out ahead of time, just in case the UN's found culpable (negligent or malicious). Then, if the UN's guilty, deduct the amount from the aid and support given by the UN--include the hours that UN staffers and troops worked at a wage comparable to similar jobs in their home country. If more is owed, then countries like the US, Nigeria, and Sri Lanka can pay more dues to cover the difference.
If what was "contributed" exceeds damages, have Haiti reimburse the UN. On the same payment schedule. And make sure to include payment for any injuries, illness, or death suffered by UN troops. Can't be hypocritical about this.
Then we can just call it even. They don't like the altruistic urge to help, even if the "good Samaritan" causes trouble? Then they obviously should make a point of rejecting such help in the future.