the word for the wrong actor [closed]

Solution 1:

The usual way to say

Kim is the wrong actor for that part or role.

is

Kim is miscast in that role.

Lexico has miscast as a verb, above is the adjectival use of the verb.

miscast
VERB

1 Allot an unsuitable role to (an actor)
he is badly miscast in the romantic lead

Lexico does not classify miscast as a noun and it would be very unusual to say

Kim is a miscast.

as if there is a similarity with misfit, which anyway is not used in this context.