It's sometimes possible for a red kite to attack and kill a chicken but it's rare that the red kite will kill or attack a chicken.
Red Kites are usually too weak footed to be able to attack any chickens or anything larger than a bunny rabbit.
If your chickens are being killed or attacked at night it's most likely some other animal such as a Weasel which will come in at night and attack chickens and take them out one by one.
The weasel will come back over and over again usually the next night and kill another chicken and take off with them.
Weasels usually work alone and are very strong so they can tear through chicken wire or loose boards and attack and take off with your chickens.