Unkempt means untidy and not caring about yourself. It is an adjective  meaning shabby and sloppy (used often to describe a persons appearance)

Rumpled is the past tense of the verb rumple

It means to crumple or crush (such as a sheet of paper can be rumpled)

It can also be used meaning to ruffle or tousle someones hair.

"Rumpled" applies more to things, and "unkempt" to persons.