The deer don't seem to touch it here, whereas virtually nothing else escapes their attention.
At first we might think Nigella since lacy foliage and petals but N. sativa is annual so not that. In perennials we think the Pink/Carnation family which have that funny habit of going brown and closing up on dying flowers. For most Dianthus flowers they are rarely that deeply cut in the petals except the "Dancing Geisha" types which are enormously cut and not like this flower. So this brings us to the Ragged Robin or Lychnis flos-cuculi (in carnation family, I won't give a link, most appear to be commercial) which has this type of cut petal and consensus is that it is deer proof.