Determine if input word can be created from a list of letters
Imports

In general, imports should be listed at the top of the script, not inside function definitions.  So instead of this:

def validate_word(words, letters):
    from collections import Counter
    ...


Write:

from collections import Counter

def validate_word(words, letters):
    ...


Variable names

In Python, variable names should be snake_case.  Words beginning with upper case letters are reserved from classes, like Counter, so Count should be called count.

Test Code

user_word and letters are declared far from the code that uses them.  They should be declared near where they are used, so at the bottom of the script, and ideally inside a __name__ == '__main__' guard:

from collections import Counter

def validate_word(word, letters):
    ...

if __name__ == '__main__':
    user_word = 'BANANA'
    letters = ['N', 'B', 'N', 'A', 'A', 'P', 'M', 'S', 'A']
    print(validate_word(user_word, letters))


A String is a List of Characters

The Counter class accepts an iterable for its construction argument, such as the list of letters you want to count.  But a string is also an iterable list of characters, so instead of a list, you could simply pass in a string, and it would work just as well:

if __name__ == '__main__':
    user_word = 'BANANA'
    letters = 'NBNAAPMSA'
    print(validate_word(user_word, letters))


Counters

You are counting up the counts of letters you are allowed to use.  Why not count up the count of letters in the user_word?

&gt;&gt;&gt; Counter('NBNAAPMSA')
Counter({'A': 3, 'N': 2, 'B': 1, 'P': 1, 'M': 1, 'S': 1})
&gt;&gt;&gt; Counter('BANANA')
Counter({'A': 3, 'N': 2, 'B': 1})


Then instead of looping over the letters of the user word, and subtracting 1 from the letter count, you could compare the letter counts directly.

Or ... you could subtract one from the other ...

&gt;&gt;&gt; counts = Counter('NBNAAPMSA')
&gt;&gt;&gt; counts.subtract('BANANA')
&gt;&gt;&gt; counts
Counter({'P': 1, 'M': 1, 'S': 1, 'N': 0, 'B': 0, 'A': 0})
&gt;&gt;&gt; 


As long as all values in the counter are non-negative, the word is valid.

&gt;&gt;&gt; all(count &gt;= 0 for count in counts.values())
True


From this, a simpler function can be created.  Left to student.