‘Unkempt’ means ‘neglected’, and it’s usually used to describe people or property (buildings and yards or gardens).
“John always comes to his 8:00 AM class with messy hair and wrinkled clothes; he looks so unkempt!”
‘Unkempt’ is the correct spelling of the word to describe people with a messy, untidy appearance.
“Jan always looks unkempt, like he’s been playing video games all night and hasn’t slept or showered.”
There aren’t many words in English that have the consonant sounds ‘m-p-t’ together, and they feel rather awkward to say in a bunch. That’s most likely why the ‘m’ tends to slip away when people say or try to spell the word.
‘Unkept’ means ‘not kept’. For example, we talk about ‘keeping a promise’. If you don’t keep your promises, then they are unkept. “Their friendship fell apart due to unkept promises.” This word isn’t used very often.