Let's talk Agent 47 and Diana Burnwood!

[Cyvanix]

They both certainly care for each other and Agent 47 had a contract to kill her but refused to do so, maybe it was because he have developed feelings for her over the years or since they have been business partners for so long and she is way too valuable to lose.
Diana also had the chance to kill Agent 47 in Blood Money but decided fake his death ;)
It wouldn't make any sense either why they should just kill each other and let's face it they need each other! :)